Average Weather in Wilmington Delaware, United States
In Wilmington, the summers are warm and humid, the winters are very cold, and it is wet and partly cloudy year round. Over the course of the year, the temperature typically varies from 26°F to 86°F and is rarely below 13°F or above 93°F.
Based on the tourism score, the best times of year to visit Wilmington for warm-weather activities are from early June to early July and from early August to late September.
The hot season lasts for 3.6 months, from May 30 to September 17, with an average daily high temperature above 77°F. The hottest day of the year is July 21, with an average high of 86°F and low of 70°F.
The cold season lasts for 3.1 months, from December 3 to March 7, with an average daily high temperature below 49°F. The coldest day of the year is January 30, with an average low of 26°F and high of 40°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 Wilmington, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.
The clearer part of the year in Wilmington begins around June 25 and lasts for 4.7 months, ending around November 14. On August 28, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 64% of the time, and overcast or mostly cloudy 35% of the time.
The cloudier part of the year begins around November 14 and lasts for 7.3 months, ending around June 25. On December 24, the cloudiest day of the year, the sky is overcast or mostly cloudy 53% of the time, and clear, mostly clear, or partly cloudy 47% 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 in Wilmington varies throughout the year.
The wetter season lasts 4.9 months, from March 31 to August 27, with a greater than 30% chance of a given day being a wet day. The chance of a wet day peaks at 38% on July 15.
The drier season lasts 7.1 months, from August 27 to March 31. The smallest chance of a wet day is 22% on October 20.
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 38% on July 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. Wilmington experiences some seasonal variation in monthly rainfall.
Rain falls throughout the year in Wilmington. The most rain falls during the 31 days centered around September 27, with an average total accumulation of 3.7 inches.
The least rain falls around February 7, with an average total accumulation of 2.1 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. Wilmington experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.1 months, from November 23 to March 27, 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 27, with an average total liquid-equivalent accumulation of 0.7 inches.
The snowless period of the year lasts for 7.9 months, from March 27 to November 23. The least snow falls around July 27, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Wilmington varies significantly over the course of the year. In 2019, the shortest day is December 21, with 9 hours, 21 minutes of daylight; the longest day is June 21, with 14 hours, 59 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:33 AM on June 14, and the latest sunrise is 1 hour, 58 minutes later at 7:31 AM on November 2. The earliest sunset is at 4:37 PM on December 8, and the latest sunset is 3 hours, 57 minutes later at 8:34 PM on June 28.
Daylight saving time (DST) is observed in Wilmington during 2019, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.
Sunrise & Sunset with Twilight and Daylight Saving Time
Wilmington experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 4.0 months, from May 26 to September 27, during which time the comfort level is muggy, oppressive, or miserable at least 16% of the time. The muggiest day of the year is July 29, with muggy conditions 62% of the time.
The least muggy day of the year is February 11, 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 in Wilmington experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.5 months, from October 26 to May 8, with average wind speeds of more than 7.4 miles per hour. The windiest day of the year is February 26, with an average hourly wind speed of 9.3 miles per hour.
The calmer time of year lasts for 5.5 months, from May 8 to October 26. The calmest day of the year is August 13, with an average hourly wind speed of 5.5 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Wilmington varies throughout the year.
The wind is most often from the south for 3.0 weeks, from June 4 to June 25 and for 2.5 months, from July 22 to October 6, with a peak percentage of 36% on August 2. The wind is most often from the west for 3.9 weeks, from June 25 to July 22 and for 7.9 months, from October 6 to June 4, with a peak percentage of 37% on July 8.
Wilmington is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average water temperature experiences significant seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.5 months, from June 19 to October 3, with an average temperature above 67°F. The day of the year with the warmest water is August 7, with an average temperature of 75°F.
The time of year with cooler water lasts for 3.6 months, from December 21 to April 7, with an average temperature below 46°F. The day of the year with the coolest water is February 16, with an average temperature of 39°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Wilmington 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 times of year to visit Wilmington for general outdoor tourist activities are from early June to early July and from early August to late September, with a peak score in the first week of September.
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 Wilmington for hot-weather activities is from late June to late August, with a peak score in the last 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 Wilmington typically lasts for 7.1 months (218 days), from around April 2 to around November 7, rarely starting before March 17 or after April 19, and rarely ending before October 22 or after November 23.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Wilmington should appear around April 2, only rarely appearing before March 18 or after April 16.
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 3.8 months, from April 28 to August 22, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is June 27, with an average of 6.9 kWh.
The darker period of the year lasts for 3.1 months, from November 6 to February 9, with an average daily incident shortwave energy per square meter below 2.9 kWh. The darkest day of the year is December 23, with an average of 1.9 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Wilmington are 39.746 deg latitude, -75.547 deg longitude, and 62 ft elevation.
The topography within 2 miles of Wilmington contains only modest variations in elevation, with a maximum elevation change of 279 feet and an average elevation above sea level of 68 feet. Within 10 miles also contains only modest variations in elevation (479 feet). Within 50 miles contains only modest variations in elevation (1,211 feet).
The area within 2 miles of Wilmington is covered by artificial surfaces (96%), within 10 miles by artificial surfaces (52%) and trees (24%), and within 50 miles by cropland (34%) and trees (31%).
This report illustrates the typical weather in Wilmington, 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 Wilmington.
For each station, the records are corrected for the elevation difference between that station and Wilmington 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 Wilmington is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Wilmington and a given station.
The stations contributing to this reconstruction are: New Castle Airport (79%, 9 kilometers, southwest); Philadelphia International Airport (13%, 31 kilometers, northeast); and Chester County G O Carlson Airport (8%, 38 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .