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Average Weather at Helena Regional Airport Montana, United States

At Helena Regional Airport, the summers are short, warm, and mostly clear; the winters are freezing and partly cloudy; and it is dry year round. Over the course of the year, the temperature typically varies from 14°F to 86°F and is rarely below -6°F or above 95°F.

Based on the tourism score, the best time of year to visit Helena Regional Airport for warm-weather activities is from early July to mid August.

Climate Summary

very coldcoldcoolwarmhotwarmcoolcoldvery coldJanFebMarAprMayJunJulAugSepOctNovDec77%77%36%36%clearovercastprecipitation: 2.4 inprecipitation: 2.4 in0.3 in0.3 inmuggy: 0%muggy: 0%0%0%drydrytourism score: 6.8tourism score: 6.80.00.0
Click on each chart for more information.

Temperature

The hot season lasts for 2.8 months, from June 16 to September 10, with an average daily high temperature above 75°F. The hottest day of the year is July 27, with an average high of 86°F and low of 56°F.

The cold season lasts for 3.2 months, from November 18 to February 25, with an average daily high temperature below 42°F. The coldest day of the year is January 1, with an average low of 14°F and high of 31°F.

Average High and Low Temperature

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 Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMfreezingfreezingvery coldcoldcoldcoolwarmvery coldcomfortablecomfortable
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 average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Kelkit, Turkey (6,197 miles away); Fareydūnshahr, Iran (6,836 miles); and Tagob, Tajikistan (6,540 miles) are the far-away foreign places with temperatures most similar to Helena Regional Airport (view comparison).

Clouds

At Helena Regional 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 Helena Regional Airport begins around June 16 and lasts for 3.7 months, ending around October 7. On July 23, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 77% of the time, and overcast or mostly cloudy 23% of the time.

The cloudier part of the year begins around October 7 and lasts for 8.3 months, ending around June 16. On March 19, the cloudiest day of the year, the sky is overcast or mostly cloudy 64% of the time, and clear, mostly clear, or partly cloudy 36% of the time.

Cloud Cover Categories

Cloud Cover Categories at Helena Regional AirportclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Jul 2377%Jul 2377%Mar 1936%Mar 1936%Jun 1656%Jun 1656%Oct 757%Oct 757%clearmostly clearpartly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

Precipitation

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

The wetter season lasts 2.0 months, from May 3 to July 4, with a greater than 22% chance of a given day being a wet day. The chance of a wet day peaks at 36% on June 3.

The drier season lasts 10.0 months, from July 4 to May 3. The smallest chance of a wet day is 7% on February 5.

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 Helena Regional Airport changes throughout the year.

Rain alone is the most common for 9.5 months, from February 17 to December 3. The highest chance of a day with rain alone is 36% on June 3.

Snow alone is the most common for 2.5 months, from December 3 to February 17. The highest chance of a day with snow alone is 6% on December 27.

Daily Chance of Precipitation

Daily Chance of Precipitation at Helena Regional AirportsnowrainsnowJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jun 336%Jun 336%Feb 57%Feb 57%Dec 312%Dec 312%May 322%May 322%Jul 422%Jul 422%rainsnowmixed
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. Helena Regional Airport experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 7.2 months, from March 22 to October 29, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around June 2, with an average total accumulation of 2.4 inches.

The rainless period of the year lasts for 4.8 months, from October 29 to March 22. The least rain falls around January 29, with an average total accumulation of 0.1 inches.

Average Monthly Rainfall

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. Helena Regional Airport experiences some seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 5.5 months, from October 30 to April 13, 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 30, with an average total liquid-equivalent accumulation of 0.3 inches.

The snowless period of the year lasts for 6.5 months, from April 13 to October 30. The least snow falls around July 25, with an average total liquid-equivalent accumulation of 0.0 inches.

Average Liquid-Equivalent Monthly Snowfall

Average Liquid-Equivalent Monthly Snowfall at Helena Regional AirportsnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0.0 in0.5 in1.0 in1.5 in2.0 in2.5 inDec 300.3 inDec 300.3 inJul 250.0 inJul 250.0 inOct 300.1 inOct 300.1 inApr 130.1 inApr 130.1 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 Helena Regional Airport varies significantly over the course of the year. In 2018, the shortest day is December 21, with 8 hours, 34 minutes of daylight; the longest day is June 21, with 15 hours, 50 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight at Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 2012 hr, 7 minMar 2015 hr, 50 minJun 2115 hr, 50 minJun 2112 hr, 10 minSep 2212 hr, 10 minSep 228 hr, 34 minDec 218 hr, 34 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 5:33 AM on June 16, and the latest sunrise is 2 hours, 39 minutes later at 8:12 AM on November 3. The earliest sunset is at 4:40 PM on December 10, and the latest sunset is 4 hours, 45 minutes later at 9:25 PM on June 26.

Daylight saving time (DST) is observed at Helena Regional Airport during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.

Sunrise & Sunset with Twilight and Daylight Saving Time

Sunrise & Sunset with Twilight and Daylight Saving Time at Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 165:33 AMJun 165:33 AM9:25 PMJun 269:25 PMJun 26Dec 104:40 PMDec 104:40 PM8:12 AMNov 38:12 AMNov 3Mar 11DSTMar 11DSTDSTNov 4DSTNov 4daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2018. 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 Helena Regional 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 Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Dec 270%Dec 270%Jun 240%Jun 240%drydry
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

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 Helena Regional Airport experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.2 months, from October 7 to May 14, with average wind speeds of more than 6.4 miles per hour. The windiest day of the year is January 17, with an average hourly wind speed of 7.6 miles per hour.

The calmer time of year lasts for 4.8 months, from May 14 to October 7. The calmest day of the year is August 5, with an average hourly wind speed of 5.1 miles per hour.

Average Wind Speed

Average Wind Speed at Helena Regional AirportwindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph2 mph4 mph6 mph8 mph10 mph12 mphJan 177.6 mphJan 177.6 mphAug 55.1 mphAug 55.1 mphOct 76.4 mphOct 76.4 mphMay 146.4 mphMay 146.4 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 Helena Regional Airport is from the west throughout the year.

Wind Direction

Wind Direction at Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 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 Helena Regional 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 Helena Regional Airport for general outdoor tourist activities is from early July to mid August, with a peak score in the last week of July.

Tourism Score

Tourism Score at Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec02468106.86.80.00.0precipitationprecipitationcloudscloudstemperaturetemperaturetourism 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 Helena Regional Airport for hot-weather activities is from mid July to mid August, with a peak score in the last week of July.

Beach/Pool Score

Beach/Pool Score at Helena Regional AirportJanFebMarAprMayJunJulAugSepOctNovDec02468103.53.50.00.0 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 Helena Regional Airport typically lasts for 4.6 months (142 days), from around May 9 to around September 28, rarely starting before April 21 or after May 31, and rarely ending before September 9 or after October 16.

Time Spent in Various Temperature Bands and the Growing Season

Time Spent in Various Temperature Bands and the Growing Season at Helena Regional Airportgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%May 950%May 950%Sep 2850%Sep 2850%May 3190%May 3190%Sep 990%Sep 990%Apr 2110%Apr 2110%Oct 1610%Oct 1610%0%Feb 160%Feb 16Jul 19100%Jul 19100%frigidfreezingvery coldcoolwarmcoldcomfortablehot
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 percentage of time spent in various temperature bands. 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 Helena Regional Airport should appear around April 27, only rarely appearing before April 15 or after May 11.

Growing Degree Days

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 3.1 months, from May 17 to August 21, with an average daily incident shortwave energy per square meter above 6.4 kWh. The brightest day of the year is July 8, with an average of 7.6 kWh.

The darker period of the year lasts for 3.5 months, from October 29 to February 13, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest day of the year is December 24, with an average of 1.4 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy at Helena Regional AirportbrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWh9 kWh10 kWhJul 87.6 kWhJul 87.6 kWhDec 241.4 kWhDec 241.4 kWhMay 176.4 kWhMay 176.4 kWhAug 216.4 kWhAug 216.4 kWhOct 292.6 kWhOct 292.6 kWhFeb 132.6 kWhFeb 132.6 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 Helena Regional Airport are 46.607 deg latitude, -111.983 deg longitude, and 3,858 ft elevation.

The topography within 2 miles of Helena Regional Airport contains significant variations in elevation, with a maximum elevation change of 492 feet and an average elevation above sea level of 3,869 feet. Within 10 miles contains significant variations in elevation (2,900 feet). Within 50 miles contains large variations in elevation (6,371 feet).

The area within 2 miles of Helena Regional Airport is covered by grassland (40%), shrubs (28%), cropland (20%), and artificial surfaces (12%), within 10 miles by grassland (35%) and shrubs (27%), and within 50 miles by grassland (29%) and trees (27%).

Data Sources

This report illustrates the typical weather at Helena Regional 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

Helena Regional 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 are Bert Mooney Airport, Great Falls International Airport, Gallatin Field Airport, Malmstrom Air Force Base, Dillon Airport, Mission Field, and Lewistown Municipal 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.