1. WeatherSpark.com
  2. United States
  3. Colorado
  4. Boulder Municipal Airport

Average Weather at Boulder Municipal Airport Colorado, United States

At Boulder Municipal Airport, the summers are warm; the winters are very cold, dry, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 22°F to 88°F and is rarely below 6°F or above 96°F.

Climate Summary

coldcoolwarmhotwarmcoolcoldJanFebMarAprMayJunJulAugSepOctNovDec74%74%53%53%clearovercastprecipitation: 1.9 inprecipitation: 1.9 in0.3 in0.3 inmuggy: 0%muggy: 0%0%0%drydrytourism score: 7.1tourism score: 7.10.30.3
Click on each chart for more information.

Based on the tourism score, the best time of year to visit Boulder Municipal Airport for warm-weather activities is from mid June to early September.

Temperature

The hot season lasts for 3.1 months, from June 8 to September 13, with an average daily high temperature above 79°F. The hottest day of the year is July 13, with an average high of 88°F and low of 61°F.

The cold season lasts for 3.5 months, from November 17 to March 3, with an average daily high temperature below 52°F. The coldest day of the year is December 30, with an average low of 22°F and high of 43°F.

Average High and Low Temperature

Average High and Low Temperature at Boulder Municipal AirporthotcoldcoldJanFebMarAprMayJunJulAugSepOctNovDec0°F10°F20°F30°F40°F50°F60°F70°F80°F90°F100°FDec 3043°FDec 3043°FJul 1388°FJul 1388°F22°F22°F61°F61°FJun 879°FJun 879°FSep 1379°FSep 1379°FMar 352°FMar 352°F53°F53°F52°F52°F30°F30°F29°F29°FLowHigh
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

Average Hourly Temperature at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMfreezingfreezingvery coldvery coldcoldcoldcoolcomfortablewarmcomfortablefreezingfreezing
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Ankara, Turkey (6,321 miles away) is the far-away foreign place with temperatures most similar to Boulder Municipal Airport (view comparison).

Clouds

At Boulder Municipal Airport, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year at Boulder Municipal Airport begins around June 3 and lasts for 5.0 months, ending around November 1. On September 13, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 74% of the time, and overcast or mostly cloudy 26% of the time.

The cloudier part of the year begins around November 1 and lasts for 7.0 months, ending around June 3. On May 5, the cloudiest day of the year, the sky is overcast or mostly cloudy 47% of the time, and clear, mostly clear, or partly cloudy 53% of the time.

Cloud Cover Categories

Cloud Cover Categories at Boulder Municipal AirportclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Sep 1374%Sep 1374%May 553%May 553%Jun 363%Jun 363%Nov 163%Nov 163%clearmostly clearpartly cloudymostly cloudyovercast
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Boulder Municipal Airport varies throughout the year.

The wetter season lasts 5.2 months, from March 28 to September 2, with a greater than 18% chance of a given day being a wet day. The chance of a wet day peaks at 29% on July 22.

The drier season lasts 6.8 months, from September 2 to March 28. The smallest chance of a wet day is 8% on January 11.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation at Boulder Municipal Airport changes throughout the year.

Rain alone is the most common for 9.4 months, from February 17 to November 29. The highest chance of a day with rain alone is 29% on July 22.

Snow alone is the most common for 2.6 months, from November 29 to February 17. The highest chance of a day with snow alone is 5% on December 12.

Daily Chance of Precipitation

Daily Chance of Precipitation at Boulder Municipal AirportsnowrainsnowJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jul 2229%Jul 2229%Jan 118%Jan 118%Feb 1711%Feb 1711%Nov 2910%Nov 2910%Mar 2818%Mar 2818%Sep 218%Sep 218%rainmixedsnow
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Boulder Municipal Airport experiences some seasonal variation in monthly rainfall.

The rainy period of the year lasts for 8.0 months, from March 4 to November 5, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around May 15, with an average total accumulation of 1.9 inches.

The rainless period of the year lasts for 4.0 months, from November 5 to March 4. The least rain falls around December 27, with an average total accumulation of 0.1 inches.

Average Monthly Rainfall

Average Monthly Rainfall at Boulder Municipal AirportrainJanFebMarAprMayJunJulAugSepOctNovDec0.0 in0.5 in1.0 in1.5 in2.0 in2.5 in3.0 in3.5 in4.0 inMay 151.9 inMay 151.9 inDec 270.1 inDec 270.1 inJul 281.5 inJul 281.5 inMar 40.5 inMar 40.5 inNov 50.5 inNov 50.5 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Snowfall

We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Boulder Municipal Airport experiences some seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 6.6 months, from October 12 to April 30, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around December 21, with an average total liquid-equivalent accumulation of 0.3 inches.

The snowless period of the year lasts for 5.5 months, from April 30 to October 12. The least snow falls around July 19, with an average total liquid-equivalent accumulation of 0.0 inches.

Average Liquid-Equivalent Monthly Snowfall

Average Liquid-Equivalent Monthly Snowfall at Boulder Municipal AirportsnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0.0 in0.5 in1.0 in1.5 in2.0 inDec 210.3 inDec 210.3 inJul 190.0 inJul 190.0 inFeb 100.2 inFeb 100.2 inOct 120.1 inOct 120.1 inApr 300.1 inApr 300.1 in
The average liquid-equivalent snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Sun

The length of the day at Boulder Municipal Airport varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 19 minutes of daylight; the longest day is June 20, with 15 hours, 1 minute of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 2012 hr, 7 minMar 2015 hr, 1 minJun 2015 hr, 1 minJun 2012 hr, 9 minSep 2212 hr, 9 minSep 229 hr, 19 minDec 219 hr, 19 minDec 21nightnightday
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 5:31 AM on June 14, and the latest sunrise is 2 hours, 3 minutes later at 7:33 AM on November 4. The earliest sunset is at 4:35 PM on December 7, and the latest sunset is 3 hours, 59 minutes later at 8:33 PM on June 27.

Daylight saving time (DST) is observed at Boulder Municipal Airport during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.

Sunrise & Sunset with Twilight and Daylight Saving Time

Sunrise & Sunset with Twilight and Daylight Saving Time at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 145:31 AMJun 145:31 AM8:33 PMJun 278:33 PMJun 27Dec 74:35 PMDec 74:35 PM7:33 AMNov 47:33 AMNov 4Mar 12DSTMar 12DSTDSTNov 5DSTNov 5daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level at Boulder Municipal Airport, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.

Humidity Comfort Levels

Humidity Comfort Levels at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jan 200%Jan 200%Jul 210%Jul 210%drydryhumidhumid
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at Boulder Municipal Airport experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 5.2 months, from November 13 to April 18, with average wind speeds of more than 8.0 miles per hour. The windiest day of the year is January 17, with an average hourly wind speed of 10.1 miles per hour.

The calmer time of year lasts for 6.8 months, from April 18 to November 13. The calmest day of the year is August 19, with an average hourly wind speed of 6.0 miles per hour.

Average Wind Speed

Average Wind Speed at Boulder Municipal AirportwindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph2 mph4 mph6 mph8 mph10 mph12 mph14 mph16 mphJan 1710.1 mphJan 1710.1 mphAug 196.0 mphAug 196.0 mphNov 138.0 mphNov 138.0 mphApr 188.0 mphApr 188.0 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction at Boulder Municipal Airport is from the west throughout the year.

Wind Direction

Wind Direction at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westeastnorthsouth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Best Time of Year to Visit

To characterize how pleasant the weather is at Boulder Municipal Airport throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Boulder Municipal Airport for general outdoor tourist activities is from mid June to early September, with a peak score in the first week of July.

Tourism Score

Tourism Score at Boulder Municipal Airportbest timeJanFebMarAprMayJunJulAugSepOctNovDec02468107.17.10.30.3 precipitationprecipitationcloudscloudstemperaturetemperaturetourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Boulder Municipal Airport for hot-weather activities is from late June to early August, with a peak score in the second week of July.

Beach/Pool Score

Beach/Pool Score at Boulder Municipal Airportbest timeJanFebMarAprMayJunJulAugSepOctNovDec02468104.74.70.00.0 precipitationprecipitationcloudscloudstemperaturetemperaturebeach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at Boulder Municipal Airport typically lasts for 5.3 months (162 days), from around May 1 to around October 10, rarely starting before April 7 or after May 20, and rarely ending before September 17 or after October 31.

Time Spent in Various Temperature Bands and the Growing Season

Time Spent in Various Temperature Bands and the Growing Season at Boulder Municipal Airportgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%May 150%May 150%Oct 1050%Oct 1050%May 2090%May 2090%Sep 1790%Sep 1790%Apr 710%Apr 710%Oct 3110%Oct 3110%Jul 19100%Jul 19100%freezingvery coldcoldcoolcomfortablewarmfrigidhot
The percentage of time spent in various temperature bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms at Boulder Municipal Airport should appear around March 24, only rarely appearing before March 6 or after April 19.

Growing Degree Days

Growing Degree Days at Boulder Municipal AirportJanFebMarAprMayJunJulAugSepOctNovDec0°F500°F1,000°F1,500°F2,000°F2,500°F3,000°FMar 2488°FMar 2488°FJun 23900°FJun 23900°FAug 21,800°FAug 21,800°FDec 313,118°FDec 313,118°F
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 2.8 months, from May 10 to August 3, with an average daily incident shortwave energy per square meter above 6.8 kWh. The brightest day of the year is June 21, with an average of 7.9 kWh.

The darker period of the year lasts for 3.2 months, from November 3 to February 10, with an average daily incident shortwave energy per square meter below 3.5 kWh. The darkest day of the year is December 21, with an average of 2.4 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy at Boulder Municipal AirportbrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWh9 kWh10 kWhJun 217.9 kWhJun 217.9 kWhDec 212.4 kWhDec 212.4 kWhMay 106.8 kWhMay 106.8 kWhAug 36.8 kWhAug 36.8 kWhNov 33.5 kWhNov 33.5 kWhFeb 103.5 kWhFeb 103.5 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Boulder Municipal Airport are 40.039 deg latitude, -105.226 deg longitude, and 5,246 ft elevation.

The topography within 2 miles of Boulder Municipal Airport contains only modest variations in elevation, with a maximum elevation change of 256 feet and an average elevation above sea level of 5,238 feet. Within 10 miles contains only modest variations in elevation (3,806 feet). Within 50 miles also contains extreme variations in elevation (9,751 feet).

The area within 2 miles of Boulder Municipal Airport is covered by shrubs (33%), artificial surfaces (26%), cropland (25%), and grassland (11%), within 10 miles by shrubs (26%) and grassland (22%), and within 50 miles by trees (36%) and grassland (21%).

Data Sources

This report illustrates the typical weather at Boulder Municipal Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

Boulder Municipal Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back include but are not limited to Vance Brand Airport; Rocky Mountain Metropolitan Airport; Erie Municipal; Denver / Stapleton International, Co.; Fort Collins-Loveland Municipal Airport; Buckley Air Force Base; Arapahoe County Airport; and Denver International Airport.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.