Average Weather in De Witt Iowa, United States
In De Witt, the summers are long, warm, and wet; the winters are freezing, dry, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 14°F to 84°F and is rarely below -6°F or above 92°F.
Based on the tourism score, the best time of year to visit De Witt for warm-weather activities is from mid June to mid September.
The warm season lasts for 4.1 months, from May 18 to September 21, with an average daily high temperature above 73°F. The hottest day of the year is July 19, with an average high of 84°F and low of 65°F.
The cold season lasts for 3.1 months, from November 30 to March 1, with an average daily high temperature below 40°F. The coldest day of the year is January 22, with an average low of 14°F and high of 29°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
Vostochny, Russia (5,866 miles away); Aghavnadzor, Armenia (6,160 miles); and Koksan, North Korea (6,404 miles) are the far-away foreign places with temperatures most similar to De Witt (view comparison).
In De Witt, 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 in De Witt begins around June 10 and lasts for 4.5 months, ending around October 26. On August 26, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 69% of the time, and overcast or mostly cloudy 31% of the time.
The cloudier part of the year begins around October 26 and lasts for 7.5 months, ending around June 10. On December 29, the cloudiest day of the year, the sky is overcast or mostly cloudy 57% of the time, and clear, mostly clear, or partly cloudy 43% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in De Witt varies throughout the year.
The wetter season lasts 5.6 months, from April 6 to September 24, with a greater than 27% chance of a given day being a wet day. The chance of a wet day peaks at 41% on June 15.
The drier season lasts 6.4 months, from September 24 to April 6. The smallest chance of a wet day is 12% on January 28.
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 in De Witt changes throughout the year.
Rain alone is the most common for 11 months, from February 6 to December 28. The highest chance of a day with rain alone is 41% on June 15.
Snow alone is the most common for 1.3 months, from December 28 to February 6. The highest chance of a day with snow alone is 7% on January 15.
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. De Witt experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 11 months, from February 1 to January 7, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around June 16, with an average total accumulation of 4.2 inches.
The rainless period of the year lasts for 3.5 weeks, from January 7 to February 1. The least rain falls around January 21, with an average total accumulation of 0.4 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. De Witt experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.5 months, from November 14 to March 28, 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 27, with an average total liquid-equivalent accumulation of 0.4 inches.
The snowless period of the year lasts for 7.5 months, from March 28 to November 14. The least snow falls around July 30, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in De Witt varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 8 minutes of daylight; the longest day is June 21, with 15 hours, 13 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:26 AM on June 14, and the latest sunrise is 2 hours, 10 minutes later at 7:36 AM on November 3. The earliest sunset is at 4:31 PM on December 8, and the latest sunset is 4 hours, 10 minutes later at 8:41 PM on June 27.
Daylight saving time (DST) is observed in De Witt 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
De Witt experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.4 months, from June 3 to September 17, during which time the comfort level is muggy, oppressive, or miserable at least 12% of the time. The muggiest day of the year is July 21, with muggy conditions 48% of the time.
The least muggy day of the year is February 19, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
The average hourly wind speed in De Witt experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.7 months, from October 4 to May 25, with average wind speeds of more than 10.0 miles per hour. The windiest day of the year is March 23, with an average hourly wind speed of 12.4 miles per hour.
The calmer time of year lasts for 4.3 months, from May 25 to October 4. The calmest day of the year is August 3, with an average hourly wind speed of 7.6 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in De Witt varies throughout the year.
The wind is most often from the north for 2.3 months, from February 9 to April 18, with a peak percentage of 33% on March 8. The wind is most often from the south for 7.2 months, from April 18 to November 23, with a peak percentage of 38% on September 6. The wind is most often from the west for 2.5 months, from November 23 to February 9, with a peak percentage of 35% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in De Witt 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 De Witt for general outdoor tourist activities is from mid June to mid September, with a peak score in the second 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 De Witt for hot-weather activities is from late June to mid 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 in De Witt typically lasts for 5.7 months (174 days), from around April 20 to around October 11, rarely starting before April 1 or after May 8, and rarely ending before September 23 or after October 29.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in De Witt should appear around April 12, only rarely appearing before March 31 or after April 27.
Growing Degree Days
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 3.6 months, from May 4 to August 23, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is July 1, with an average of 7.0 kWh.
The darker period of the year lasts for 3.3 months, from November 1 to February 10, with an average daily incident shortwave energy per square meter below 2.8 kWh. The darkest day of the year is December 21, with an average of 1.7 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of De Witt are 41.823 deg latitude, -90.538 deg longitude, and 673 ft elevation.
The topography within 2 miles of De Witt contains only modest variations in elevation, with a maximum elevation change of 157 feet and an average elevation above sea level of 682 feet. Within 10 miles also contains only modest variations in elevation (315 feet). Within 50 miles contains only modest variations in elevation (774 feet).
The area within 2 miles of De Witt is covered by cropland (82%) and artificial surfaces (17%), within 10 miles by cropland (92%), and within 50 miles by cropland (87%).
This report illustrates the typical weather in De Witt, 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in De Witt.
For each station, the records are corrected for the elevation difference between that station and De Witt 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 De Witt is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between De Witt and a given station.
The stations contributing to this reconstruction are: Clinton Municipal Airport (54%, 17 kilometers, east); Davenport Municipal Airport (33%, 24 kilometers, south); Dubuque Regional Airport (7%, 65 kilometers, north); and Monticello Municipal (7%, 68 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .