Average Weather at St. Charles, St. Charles County Smartt Airport Missouri, United States
At St. Charles, St. Charles County Smartt Airport, the summers are hot and muggy; the winters are short, very cold, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 23°F to 89°F and is rarely below 7°F or above 96°F.
Based on the tourism score, the best time of year to visit St. Charles, St. Charles County Smartt Airport for warm-weather activities is from late May to late September.
The hot season lasts for 3.8 months, from May 25 to September 19, with an average daily high temperature above 79°F. The hottest day of the year is July 20, with an average high of 89°F and low of 70°F.
The cold season lasts for 3.0 months, from November 29 to February 27, with an average daily high temperature below 49°F. The coldest day of the year is January 22, with an average low of 23°F and high of 39°F.
Average High and Low Temperature
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
At St. Charles, St. Charles County Smartt 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 St. Charles, St. Charles County Smartt Airport begins around June 13 and lasts for 4.5 months, ending around October 28. On August 26, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 71% of the time, and overcast or mostly cloudy 29% of the time.
The cloudier part of the year begins around October 28 and lasts for 7.5 months, ending around June 13. On February 12, the cloudiest day of the year, the sky is overcast or mostly cloudy 55% of the time, and clear, mostly clear, or partly cloudy 45% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at St. Charles, St. Charles County Smartt Airport varies throughout the year.
The wetter season lasts 5.7 months, from March 22 to September 13, with a greater than 28% chance of a given day being a wet day. The chance of a wet day peaks at 40% on May 26.
The drier season lasts 6.3 months, from September 13 to March 22. The smallest chance of a wet day is 15% on January 13.
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 throughout the year is rain alone, with a peak probability of 40% on May 26.
Daily Chance of Precipitation
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. St. Charles, St. Charles County Smartt Airport experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year at St. Charles, St. Charles County Smartt Airport. The most rain falls during the 31 days centered around May 17, with an average total accumulation of 4.0 inches.
The least rain falls around January 24, with an average total accumulation of 1.3 inches.
Average Monthly Rainfall
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. St. Charles, St. Charles County Smartt Airport experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 3.9 months, from November 22 to March 19, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 20, with an average total liquid-equivalent accumulation of 0.4 inches.
The snowless period of the year lasts for 8.1 months, from March 19 to November 22. The least snow falls around July 28, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day at St. Charles, St. Charles County Smartt Airport varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 26 minutes of daylight; the longest day is June 21, with 14 hours, 54 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:35 AM on June 14, and the latest sunrise is 1 hour, 56 minutes later at 7:31 AM on November 3. The earliest sunset is at 4:39 PM on December 7, and the latest sunset is 3 hours, 52 minutes later at 8:31 PM on June 28.
Daylight saving time (DST) is observed at St. Charles, St. Charles County Smartt 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
St. Charles, St. Charles County Smartt Airport experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 4.1 months, from May 20 to September 23, during which time the comfort level is muggy, oppressive, or miserable at least 18% of the time. The muggiest day of the year is July 22, with muggy conditions 71% of the time.
The least muggy day of the year is December 26, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed at St. Charles, St. Charles County Smartt Airport experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.1 months, from October 14 to May 17, with average wind speeds of more than 8.2 miles per hour. The windiest day of the year is April 1, with an average hourly wind speed of 10.4 miles per hour.
The calmer time of year lasts for 4.9 months, from May 17 to October 14. The calmest day of the year is July 31, with an average hourly wind speed of 6.0 miles per hour.
Average Wind Speed
The predominant average hourly wind direction at St. Charles, St. Charles County Smartt Airport varies throughout the year.
The wind is most often from the south for 1.3 weeks, from February 24 to March 5 and for 8.9 months, from March 12 to December 8, with a peak percentage of 42% on June 21. The wind is most often from the north for 1.0 weeks, from March 5 to March 12, with a peak percentage of 29% on March 8. The wind is most often from the west for 2.6 months, from December 8 to February 24, with a peak percentage of 35% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is at St. Charles, St. Charles County Smartt 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 St. Charles, St. Charles County Smartt Airport for general outdoor tourist activities is from late May to late September, with a peak score in the last week of August.
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 St. Charles, St. Charles County Smartt Airport for hot-weather activities is from mid June to late August, with a peak score in the third week of July.
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.
The growing season at St. Charles, St. Charles County Smartt Airport typically lasts for 6.7 months (207 days), from around April 4 to around October 27, rarely starting before March 17 or after April 20, and rarely ending before October 7 or after November 16.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms at St. Charles, St. Charles County Smartt Airport should appear around March 21, only rarely appearing before March 8 or after April 8.
Growing Degree Days
The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 4.1 months, from April 27 to August 29, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is July 2, with an average of 6.9 kWh.
The darker period of the year lasts for 3.1 months, from November 5 to February 9, with an average daily incident shortwave energy per square meter below 3.0 kWh. The darkest day of the year is December 23, with an average of 2.0 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of St. Charles, St. Charles County Smartt Airport are 38.931 deg latitude, -90.433 deg longitude, and 427 ft elevation.
The topography within 2 miles of St. Charles, St. Charles County Smartt Airport is essentially flat, with a maximum elevation change of 26 feet and an average elevation above sea level of 427 feet. Within 10 miles is essentially flat (597 feet). Within 50 miles also contains significant variations in elevation (755 feet).
The area within 2 miles of St. Charles, St. Charles County Smartt Airport is covered by cropland (81%) and herbaceous vegetation (16%), within 10 miles by cropland (51%) and trees (25%), and within 50 miles by cropland (57%) and trees (28%).
This report illustrates the typical weather at St. Charles, St. Charles County Smartt 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
St. Charles, St. Charles County Smartt 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 Lambert–St. Louis International Airport, Spirit of St Louis Airport, Saint Louis Regional Airport, Saint Louis Downtown - Parks Airport, Flying L Airport, Litchfield Municipal Airport, Pittsfield Penstone Municipal Airport, and Jacksonville Municipal Airport.
Time zones for aiports and weather stations are provided by AskGeo.com .