Average Weather in April in St. Louis Missouri, United States
In St. Louis, the month of April is characterized by rapidly rising daily high temperatures, with daily highs increasing by 10°F, from 62°F to 72°F over the course of the month, and rarely exceeding 84°F or dropping below 47°F.
Daily low temperatures increase by 9°F, from 43°F to 52°F, rarely falling below 31°F or exceeding 63°F.
For reference, on July 20, the hottest day of the year, temperatures in St. Louis typically range from 70°F to 89°F, while on January 22, the coldest day of the year, they range from 25°F to 41°F.
Average High and Low Temperature in April
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on April. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in April
The month of April in St. Louis experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 46% throughout the month. The lowest chance of overcast or mostly cloudy conditions is 45% on April 15.
The clearest day of the month is April 15, with clear, mostly clear, or partly cloudy conditions 55% of the time.
For reference, on February 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 54%, while on August 27, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 71%.
Cloud Cover in April
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In St. Louis, the chance of a wet day over the course of April is increasing, starting the month at 32% and ending it at 38%.
For reference, the year's highest daily chance of a wet day is 40% on May 21, and its lowest chance is 16% on January 16.
Probability of Precipitation in April
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during April in St. Louis is increasing, starting the month at 3.3 inches, when it rarely exceeds 5.4 inches or falls below 1.8 inches, and ending the month at 4.0 inches, when it rarely exceeds 7.7 inches or falls below 1.3 inches.
Average Monthly Rainfall in April
Over the course of April in St. Louis, the length of the day is rapidly increasing. From the start to the end of the month, the length of the day increases by 1 hour, 8 minutes, implying an average daily increase of 2 minutes, 22 seconds, and weekly increase of 16 minutes, 32 seconds.
The shortest day of the month is April 1, with 12 hours, 39 minutes of daylight and the longest day is April 30, with 13 hours, 48 minutes of daylight.
Hours of Daylight and Twilight in April
The latest sunrise of the month in St. Louis is 6:45 AM on April 1 and the earliest sunrise is 41 minutes earlier at 6:04 AM on April 30.
The earliest sunset is 7:24 PM on April 1 and the latest sunset is 28 minutes later at 7:52 PM on April 30.
Daylight saving time is observed in St. Louis during 2017, but it neither starts nor ends during April, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:36 AM and sets 14 hours, 52 minutes later, at 8:28 PM, while on December 21, the shortest day of the year, it rises at 7:15 AM and sets 9 hours, 28 minutes later, at 4:43 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in April
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 chance that a given day will be muggy in St. Louis is gradually increasing during April, rising from 0% to 4% over the course of the month.
For reference, on July 22, the muggiest day of the year, there are muggy conditions 71% of the time, while on January 1, the leasy muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in April
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 in St. Louis is gradually decreasing during April, decreasing from 5.3 miles per hour to 4.7 miles per hour over the course of the month.
For reference, on April 1, the windiest day of the year, the daily average wind speed is 5.3 miles per hour, while on July 31, the calmest day of the year, the daily average wind speed is 3.0 miles per hour.
The highest daily average wind speed during April is 5.3 miles per hour on April 1.
Average Wind Speed in April
Wind Direction in April
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 in St. Louis is gradually increasing during April, rising by 1.0 kWh, from 5.0 kWh to 6.0 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in April
For the purposes of this report, the geographical coordinates of St. Louis are 38.627 deg latitude, -90.198 deg longitude, and 446 ft elevation.
The topography within 2 miles of St. Louis contains only modest variations in elevation, with a maximum elevation change of 161 feet and an average elevation above sea level of 456 feet. Within 10 miles also contains only modest variations in elevation (308 feet). Within 50 miles contains only modest variations in elevation (892 feet).
The area within 2 miles of St. Louis is covered by artificial surfaces (88%) and water (12%), within 10 miles by artificial surfaces (66%) and cropland (22%), and within 50 miles by cropland (54%) and trees (31%).
This report illustrates the typical weather in St. Louis year round, 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
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in St. Louis.
For each station, the records are corrected for the elevation difference between that station and St. Louis according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at St. Louis is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between St. Louis and a given station.
The stations contributing to this reconstruction are: Saint Louis Downtown - Parks Airport (76%, 7 kilometers, southeast); Lambert–St. Louis International Airport (16%, 21 kilometers, northwest); and Saint Louis Regional Airport (8%, 31 kilometers, northeast).
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.