Average Weather on July 21 in Williamsport Pennsylvania, United States
On July 21, the temperature in Williamsport typically ranges from 64°F to 82°F and is rarely below 55°F or above 91°F.
For reference, on July 20, the hottest day of the year, temperatures in Williamsport typically range from 64°F to 84°F, while on January 29, the coldest day of the year, they range from 20°F to 34°F.
The coolest time of the day is from 12:45 AM to 8:15 AM, with the coldest at 5:45 AM, at which time the temperature is below 68°F three days out of four, and below 71°F nine days out of ten.
The warmest time of the day is from 12:15 PM to 7:15 PM, with the hottest at 3:45 PM, at which time the temperature is above 78°F three days out of four, and above 74°F nine days out of ten.
The day has gained half its heat by 10:15 AM and lost it again by 9:15 PM.
Average Temperature on July 21
The figure below shows you a compact characterization of the range of temperatures experienced on July 21 throughout the historical record. The horizontal axis is the time of day and the colored stacked areas indicate the percentage of hours spent in various temperature bands.
Temperature Bands on July 21
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
In Williamsport on July 21, the average percentage of the sky covered by clouds does not show significant systematic variation over the course of the day, with the percentage of time that the sky is overcast or mostly cloudy remaining about 38% throughout the day.
For reference, on January 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 63%, while on September 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.
Cloud Cover Categories on July 21
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
On average, there is a 38% chance that more than 0.04 inches of total precipitation will fall in Williamsport throughout the day on July 21, all of which can be expected to be rain.
For reference, the year's highest daily chance of precipitation is 41% on June 15, and its lowest chance is 19% on January 14.
For those 38% of years with precipitation on July 21, the chart below shows when throughout the day that precipitation is more or less likely to occur, excluding hourly accumulations of less than 0.01 inches. If precipitation were equally likely throughout the day, all hours would report 4.2% (100% divided by 24 hours).
Precipitation is most likely between 2 PM and 3 PM, and least likely between 7 AM and 8 AM.
Hourly Share of Precipitation on July 21
In Williamsport on Sunday, July 21, 2019, the Sun rises at 5:52 AM and sets 14 hours, 43 minutes later, at 8:35 PM. Solar noon is at 1:14 PM.
For reference, on June 21, the longest day of the year, the Sun rises at 5:35 AM and sets 15 hours, 9 minutes later, at 8:44 PM, while on December 22, the shortest day of the year, it rises at 7:30 AM and sets 9 hours, 12 minutes later, at 4:42 PM.
Civil twilight, the period before the Sun has risen or after the Sun has set during which time it is possible to engage in most outdoor activities without artificial lighting, begins and ends 32 minutes before sunrise and after sunset, at 5:20 AM and 9:07 PM respectively.
Nautical twilight, during which time it is possible to clearly discern the horizon (e.g., for navigational purposes), begins and ends 1 hour, 13 minutes before sunrise and after sunset, at 4:40 AM and 9:47 PM respectively.
Astronomical twilight, outside of which it is possible to make the most sensitive of astronomical observations, begins and ends 1 hour, 58 minutes before sunrise and after sunset, at 3:54 AM and 10:33 PM respectively.
Solar Elevation on July 21, 2019
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 of muggy, oppressive, or miserable conditions in Williamsport on July 21 varies over the course of the day, with an average daily chance of 39%.
The muggiest time of day on July 21 is around 9:30 PM, with muggy conditions 45% of the time.
The least muggy time of day is around 6:30 AM, with muggy conditions 30% of the time.
For reference, on July 29, the muggiest day of the year, there are muggy conditions 40% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels on July 21
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 Williamsport on July 21 varies throughout the day, with a daily average of 3.4 miles per hour.
The windiest time of day is around 2:45 PM, with an average hourly wind speed of 4.2 miles per hour, mostly staying between 3.1 miles per hour and 5.4 miles per hour, and rarely falling below 2.0 miles per hour or exceeding 6.4 miles per hour.
The calmest time of day is around 7:30 AM, with an average hourly wind speed of 2.6 miles per hour, mostly staying between 2.0 miles per hour and 3.1 miles per hour, and rarely falling below 1.4 miles per hour or exceeding 3.9 miles per hour.
For reference, on February 26, the windiest day of the year, the daily average wind speed is 6.5 miles per hour, while on August 1, the calmest day of the year, the daily average wind speed is 3.3 miles per hour.
Wind Speed on July 21
Over the entire course of July 21 in Williamsport, the hourly average wind direction, in order of prevalence, is from the west (40%), south (28%), north (26%), and east (6%).
Wind Direction on July 21
Shortwave Solar Power
This section discusses the incident shortwave solar power 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 peak incident shortwave solar power per square meter is 0.80 kilowatts at around 1:00 PM.
In contrast, the corresponding value on June 30, the brightest day of the year, is 0.81 kilowatts at around 12:00 PM. The corresponding value on December 23, the darkest day of the year, is 0.29 kilowatts at around 11:15 AM.
Shortwave Solar Power on July 21
For the purposes of this report, the geographical coordinates of Williamsport are 41.241 deg latitude, -77.001 deg longitude, and 663 ft elevation.
The topography within 2 miles of Williamsport contains very significant variations in elevation, with a maximum elevation change of 1,007 feet and an average elevation above sea level of 651 feet. Within 10 miles also contains very significant variations in elevation (1,555 feet). Within 50 miles contains very significant variations in elevation (2,224 feet).
The area within 2 miles of Williamsport is covered by artificial surfaces (64%) and trees (28%), within 10 miles by trees (62%) and cropland (29%), and within 50 miles by trees (71%) and cropland (26%).
This report illustrates the typical weather in Williamsport, 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 Williamsport.
For each station, the records are corrected for the elevation difference between that station and Williamsport 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 Williamsport is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Williamsport and a given station.
The stations contributing to this reconstruction are: Williamsport-Lycoming County Airport (96%, 7 kilometers, east); Penn State University Park Airport (2.7%, 84 kilometers, southwest); and Wellsville Municipal Airport-Tarantine Field (1.4%, 127 kilometers, northwest).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports 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.