Average Weather in August in Des Moines Iowa, United States
Daily high temperatures decrease by 4°F, from 85°F to 82°F, rarely falling below 72°F or exceeding 94°F.
Daily low temperatures decrease by 5°F, from 67°F to 62°F, rarely falling below 53°F or exceeding 75°F.
For reference, on July 19, the hottest day of the year, temperatures in Des Moines typically range from 68°F to 86°F, while on January 21, the coldest day of the year, they range from 17°F to 33°F.
Average High and Low Temperature in August
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on August. 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 August
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 month of August in Des Moines experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 30% throughout the month. The lowest chance of overcast or mostly cloudy conditions is 30% on August 25.
The clearest day of the month is August 25, with clear, mostly clear, or partly cloudy conditions 70% of the time.
For reference, on February 13, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 54%, while on August 25, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 70%.
Cloud Cover Categories in August
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. In Des Moines, the chance of a wet day over the course of August is decreasing, starting the month at 35% and ending it at 31%.
For reference, the year's highest daily chance of a wet day is 43% on June 25, and its lowest chance is 8% on January 9.
Probability of Precipitation in August
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 August in Des Moines is gradually decreasing, starting the month at 3.7 inches, when it rarely exceeds 6.9 inches or falls below 1.4 inches, and ending the month at 3.4 inches, when it rarely exceeds 6.5 inches or falls below 1.3 inches.
Average Monthly Rainfall in August
Over the course of August in Des Moines, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 14 minutes, implying an average daily decrease of 2 minutes, 27 seconds, and weekly decrease of 17 minutes, 11 seconds.
The shortest day of the month is August 31, with 13 hours, 8 minutes of daylight and the longest day is August 1, with 14 hours, 22 minutes of daylight.
Hours of Daylight and Twilight in August
The earliest sunrise of the month in Des Moines is 6:09 AM on August 1 and the latest sunrise is 31 minutes later at 6:40 AM on August 31.
The latest sunset is 8:31 PM on August 1 and the earliest sunset is 43 minutes earlier at 7:48 PM on August 31.
Daylight saving time is observed in Des Moines during 2020, but it neither starts nor ends during August, so the entire month is in daylight saving time.
For reference, on June 20, the longest day of the year, the Sun rises at 5:40 AM and sets 15 hours, 12 minutes later, at 8:52 PM, while on December 21, the shortest day of the year, it rises at 7:38 AM and sets 9 hours, 10 minutes later, at 4:47 PM.
Sunrise & Sunset with Twilight in August
The figure below presents a compact representation of key lunar data for August 2020. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in August
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 Des Moines is rapidly decreasing during August, falling from 51% to 35% over the course of the month.
For reference, on July 20, the muggiest day of the year, there are muggy conditions 55% of the time, while on November 14, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in August
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 Des Moines is gradually increasing during August, increasing from 8.0 miles per hour to 8.8 miles per hour over the course of the month.
For reference, on March 31, the windiest day of the year, the daily average wind speed is 12.8 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 8.0 miles per hour.
The lowest daily average wind speed during August is 8.0 miles per hour on August 2.
Average Wind Speed in August
The hourly average wind direction in Des Moines throughout August is predominantly from the south, with a peak proportion of 44% on August 28.
Wind Direction in August
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 in Des Moines typically lasts for 6.1 months (188 days), from around April 12 to around October 16, rarely starting before March 27 or after April 28, and rarely ending before September 26 or after November 6.
The month of August in Des Moines is reliably fully within the growing season.
Time Spent in Various Temperature Bands and the Growing Season in August
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
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.
The average accumulated growing degree days in Des Moines are rapidly increasing during August, increasing by 704°F, from 2,138°F to 2,842°F, over the course of the month.
Growing Degree Days in August
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 Des Moines is gradually decreasing during August, falling by 0.9 kWh, from 6.6 kWh to 5.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in August
For the purposes of this report, the geographical coordinates of Des Moines are 41.601 deg latitude, -93.609 deg longitude, and 869 ft elevation.
The topography within 2 miles of Des Moines contains only modest variations in elevation, with a maximum elevation change of 197 feet and an average elevation above sea level of 830 feet. Within 10 miles also contains only modest variations in elevation (262 feet). Within 50 miles contains only modest variations in elevation (741 feet).
The area within 2 miles of Des Moines is covered by artificial surfaces (100%), within 10 miles by cropland (46%) and artificial surfaces (43%), and within 50 miles by cropland (88%).
This report illustrates the typical weather in Des Moines, 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 Des Moines.
For each station, the records are corrected for the elevation difference between that station and Des Moines 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 Des Moines is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Des Moines and a given station.
The stations contributing to this reconstruction are: Des Moines International Airport (56%, 8 kilometers, southwest); Ankeny Regional Airport (40%, 11 kilometers, north); and Perry Municipal Airport (3.7%, 52 kilometers, northwest).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , 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 airports 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.
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.