Average Weather in Washington Iowa, United States
In Washington, the summers are long, warm, humid, 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 17°F to 87°F and is rarely below -2°F or above 95°F.
Based on the tourism score, the best time of year to visit Washington for warm-weather activities is from early June to mid September.
The hot season lasts for 4.1 months, from May 18 to September 21, with an average daily high temperature above 76°F. The hottest day of the year is July 18, with an average high of 87°F and low of 66°F.
The cold season lasts for 3.1 months, from November 29 to March 1, with an average daily high temperature below 44°F. The coldest day of the year is January 22, with an average low of 17°F and high of 33°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
In Washington, 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 Washington begins around June 10 and lasts for 4.5 months, ending around October 26. On September 14, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 70% of the time, and overcast or mostly cloudy 30% 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 28, 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
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Washington varies throughout the year.
The wetter season lasts 6.1 months, from March 31 to October 2, with a greater than 26% chance of a given day being a wet day. The chance of a wet day peaks at 40% on June 7.
The drier season lasts 5.9 months, from October 2 to March 31. The smallest chance of a wet day is 11% 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 Washington changes throughout the year.
Rain alone is the most common for 11 months, from February 4 to January 2. The highest chance of a day with rain alone is 40% on June 7.
Snow alone is the most common for 1.1 months, from January 2 to February 4. The highest chance of a day with snow alone is 5% on December 23.
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. Washington experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 11 months, from January 30 to January 4, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around June 19, with an average total accumulation of 4.3 inches.
The rainless period of the year lasts for 3.8 weeks, from January 4 to January 30. The least rain falls around January 20, 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. Washington experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.1 months, from November 16 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 December 28, with an average total liquid-equivalent accumulation of 0.4 inches.
The snowless period of the year lasts for 7.9 months, from March 19 to November 16. The least snow falls around July 18, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Washington varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 11 minutes of daylight; the longest day is June 21, with 15 hours, 10 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:33 AM on June 14, and the latest sunrise is 2 hours, 8 minutes later at 7:40 AM on November 3. The earliest sunset is at 4:37 PM on December 8, and the latest sunset is 4 hours, 7 minutes later at 8:44 PM on June 27.
Daylight saving time (DST) is observed in Washington 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
Washington experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.7 months, from May 28 to September 19, during which time the comfort level is muggy, oppressive, or miserable at least 15% of the time. The muggiest day of the year is July 22, with muggy conditions 59% of the time.
The least muggy day of the year is December 11, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
The average hourly wind speed in Washington experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.6 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 April 1, with an average hourly wind speed of 12.5 miles per hour.
The calmer time of year lasts for 4.4 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 Washington varies throughout the year.
The wind is most often from the north for 2.0 months, from February 6 to April 7, with a peak percentage of 33% on February 19. The wind is most often from the south for 7.7 months, from April 7 to November 27, with a peak percentage of 40% on September 6. The wind is most often from the west for 2.2 months, from November 27 to February 6, with a peak percentage of 34% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in Washington 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 Washington for general outdoor tourist activities is from early June to mid 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 Washington for hot-weather activities is from late 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 in Washington typically lasts for 6.2 months (188 days), from around April 12 to around October 18, rarely starting before March 26 or after April 29, and rarely ending before September 29 or after November 5.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Washington should appear around April 5, only rarely appearing before March 22 or after April 21.
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 3.7 months, from May 2 to August 25, 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 6.9 kWh.
The darker period of the year lasts for 3.2 months, from November 2 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 1.8 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Washington are 41.299 deg latitude, -91.693 deg longitude, and 741 ft elevation.
The topography within 2 miles of Washington contains only modest variations in elevation, with a maximum elevation change of 105 feet and an average elevation above sea level of 733 feet. Within 10 miles also contains only modest variations in elevation (213 feet). Within 50 miles also contains only modest variations in elevation (463 feet).
The area within 2 miles of Washington is covered by cropland (81%) and artificial surfaces (19%), within 10 miles by cropland (95%), and within 50 miles by cropland (85%) and trees (11%).
This report illustrates the typical weather in Washington, 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Washington.
For each station, the records are corrected for the elevation difference between that station and Washington 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 Washington is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Washington and a given station.
Time zones for aiports and weather stations are provided by AskGeo.com .