Average Weather in Williamstown Pennsylvania, United States
In Williamstown, the summers are warm, humid, and wet; the winters are freezing; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 19°F to 83°F and is rarely below 5°F or above 90°F.
Based on the tourism score, the best time of year to visit Williamstown for warm-weather activities is from mid June to mid September.
The warm season lasts for 3.6 months, from May 27 to September 15, with an average daily high temperature above 73°F. The hottest day of the year is July 21, with an average high of 83°F and low of 62°F.
The cold season lasts for 3.2 months, from December 1 to March 6, with an average daily high temperature below 43°F. The coldest day of the year is January 30, with an average low of 19°F and high of 34°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 Williamstown, 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 Williamstown begins around June 16 and lasts for 4.8 months, ending around November 10. On September 4, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 65% of the time, and overcast or mostly cloudy 35% of the time.
The cloudier part of the year begins around November 10 and lasts for 7.2 months, ending around June 16. On January 11, 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 Williamstown varies throughout the year.
The wetter season lasts 4.6 months, from April 10 to August 28, with a greater than 30% chance of a given day being a wet day. The chance of a wet day peaks at 39% on June 16.
The drier season lasts 7.4 months, from August 28 to April 10. The smallest chance of a wet day is 20% 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 Williamstown changes throughout the year.
Rain alone is the most common for 11 months, from February 12 to January 6. The highest chance of a day with rain alone is 39% on June 16.
Snow alone is the most common for 1.2 months, from January 6 to February 12. The highest chance of a day with snow alone is 9% on February 1.
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. Williamstown experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Williamstown. 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 5, with an average total accumulation of 1.2 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. Williamstown experiences significant seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 5.5 months, from October 29 to April 15, 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 1.2 inches.
The snowless period of the year lasts for 6.5 months, from April 15 to October 29. The least snow falls around July 24, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Williamstown varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 16 minutes of daylight; the longest day is June 21, with 15 hours, 5 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:35 AM on June 14, and the latest sunrise is 2 hours, 4 minutes later at 7:38 AM on November 3. The earliest sunset is at 4:39 PM on December 8, and the latest sunset is 4 hours, 2 minutes later at 8:41 PM on June 27.
Daylight saving time (DST) is observed in Williamstown 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
Williamstown experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.8 months, from May 29 to September 21, during which time the comfort level is muggy, oppressive, or miserable at least 12% of the time. The muggiest day of the year is August 2, with muggy conditions 47% of the time.
The least muggy day of the year is December 7, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
The average hourly wind speed in Williamstown experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 5.5 months, from November 16 to May 1, with average wind speeds of more than 5.2 miles per hour. The windiest day of the year is February 26, with an average hourly wind speed of 6.7 miles per hour.
The calmer time of year lasts for 6.5 months, from May 1 to November 16. The calmest day of the year is August 1, with an average hourly wind speed of 3.6 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Williamstown varies throughout the year.
The wind is most often from the south for 2.0 weeks, from May 10 to May 24 and for 2.2 months, from August 1 to October 7, with a peak percentage of 35% on September 8. The wind is most often from the west for 2.3 months, from May 24 to August 1 and for 7.1 months, from October 7 to May 10, with a peak percentage of 39% on July 8.
Best Time of Year to Visit
To characterize how pleasant the weather is in Williamstown 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 Williamstown 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 Williamstown 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 Williamstown typically lasts for 5.6 months (172 days), from around April 26 to around October 15, rarely starting before April 7 or after May 17, and rarely ending before September 28 or after November 2.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Williamstown should appear around April 17, only rarely appearing before April 5 or after April 28.
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 1 to August 23, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is June 28, with an average of 6.9 kWh.
The darker period of the year lasts for 3.2 months, from November 5 to February 11, with an average daily incident shortwave energy per square meter below 2.8 kWh. The darkest day of the year is December 23, with an average of 1.7 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Williamstown are 40.580 deg latitude, -76.618 deg longitude, and 1,224 ft elevation.
The topography within 2 miles of Williamstown contains very significant variations in elevation, with a maximum elevation change of 1,083 feet and an average elevation above sea level of 1,183 feet. Within 10 miles also contains very significant variations in elevation (1,368 feet). Within 50 miles contains very significant variations in elevation (2,398 feet).
The area within 2 miles of Williamstown is covered by trees (96%), within 10 miles by trees (71%) and cropland (27%), and within 50 miles by trees (49%) and cropland (41%).
This report illustrates the typical weather in Williamstown, 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 Williamstown.
For each station, the records are corrected for the elevation difference between that station and Williamstown 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 Williamstown is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Williamstown and a given station.
The stations contributing to this reconstruction are: Muir Army Air Field / Indiantown (59%, 17 kilometers, south); Penn Valley Airport (33%, 34 kilometers, northwest); and Wilkes-Barre/Scranton International Airport (7%, 112 kilometers, northeast).
Time zones for aiports and weather stations are provided by AskGeo.com .