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Average Weather in August in Gilroy California, United States

In Gilroy, the month of August is characterized by essentially constant daily high temperatures, with daily highs around 83°F throughout the month, rarely exceeding 92°F or dropping below 75°F. The highest daily average high temperature is 83°F on August 24.

Daily low temperatures are around 55°F, rarely falling below 52°F or exceeding 60°F. The highest daily average low temperature is 55°F on August 29.

For reference, on August 23, the hottest day of the year, temperatures in Gilroy typically range from 55°F to 83°F, while on December 31, the coldest day of the year, they range from 39°F to 60°F.

Average High and Low Temperature in August

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on August. The horizontal axis is the day, 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 August

Average Hourly Temperature in August in Gilroy18152229112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM4 AM8 AM12 PM4 PM8 PM12 AMJulSepwarmcoolcoldcomfortable
The average hourly temperature, color coded into bands: 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. The shaded overlays indicate night and civil twilight.


The month of August in Gilroy experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 9% throughout the month.

The clearest day of the month is August 7, with clear, mostly clear, or partly cloudy conditions 92% of the time.

For reference, on February 4, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 54%, while on July 29, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.

Cloud Cover Categories in August

Cloud Cover Categories in August in Gilroy1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%JulSepAug 192%Aug 192%Aug 3190%Aug 3190%Aug 1191%Aug 1191%Aug 2191%Aug 2191%clearovercastmostly clearpartly cloudy
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.



Over the course of August in Gilroy, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 2 minutes, implying an average daily decrease of 2 minutes, 4 seconds, and weekly decrease of 14 minutes, 28 seconds.

The shortest day of the month is August 31, with 12 hours, 59 minutes of daylight and the longest day is August 1, with 14 hours, 1 minute of daylight.

Hours of Daylight and Twilight in August

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Gilroy is 6:11 AM on August 1 and the latest sunrise is 25 minutes later at 6:36 AM on August 31.

The latest sunset is 8:12 PM on August 1 and the earliest sunset is 37 minutes earlier at 7:35 PM on August 31.

Daylight saving time is observed in Gilroy during 2017, but it neither starts nor ends during August, so the entire month is in daylight saving time.

For reference, on June 21, the longest day of the year, the Sun rises at 5:47 AM and sets 14 hours, 42 minutes later, at 8:29 PM, while on December 21, the shortest day of the year, it rises at 7:16 AM and sets 9 hours, 37 minutes later, at 4:53 PM.

Sunrise & Sunset with Twilight in August

The solar day over the course of August. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.


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 that a given day will be muggy in Gilroy is essentially constant during August, remaining around 0% throughout.

For reference, on September 17, the muggiest day of the year, there are muggy conditions 0% 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 in August

The percentage of time spent at various humidity comfort levels, categorized by dew point: 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 Gilroy is essentially constant during August, remaining within 0.2 miles per hour of 6.7 miles per hour throughout.

For reference, on June 6, the windiest day of the year, the daily average wind speed is 8.0 miles per hour, while on November 1, the calmest day of the year, the daily average wind speed is 5.6 miles per hour.

Average Wind Speed in August

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
The hourly average wind direction in Gilroy throughout August is predominantly from the west, with a peak proportion of 95% on August 2.

Wind Direction in August

Wind Direction in August in Gilroy1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%JulSepwestnorth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Gilroy 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 surface water temperature in Gilroy is essentially constant during August, remaining around 58°F throughout.

Average Water Temperature in August

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy 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 average daily incident shortwave solar energy in Gilroy is decreasing during August, falling by 1.0 kWh, from 8.0 kWh to 7.0 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in August

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.


For the purposes of this report, the geographical coordinates of Gilroy are 37.006 deg latitude, -121.568 deg longitude, and 210 ft elevation.

The topography within 2 miles of Gilroy contains only modest variations in elevation, with a maximum elevation change of 449 feet and an average elevation above sea level of 209 feet. Within 10 miles contains only modest variations in elevation (2,740 feet). Within 50 miles contains large variations in elevation (5,046 feet).

The area within 2 miles of Gilroy is covered by artificial surfaces (64%) and cropland (29%), within 10 miles by grassland (43%) and cropland (23%), and within 50 miles by grassland (30%) and shrubs (17%).

Data Sources

This report illustrates the typical weather in Gilroy year round, 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 Gilroy.

For each station, the records are corrected for the elevation difference between that station and Gilroy 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 Gilroy is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Gilroy and a given station.

The stations contributing to this reconstruction are: Hollister Municipal Airport (48%, 18 kilometers, southeast); Watsonville Municipal Airport (37%, 21 kilometers, west); Norman Y. Mineta San José International Airport (10%, 50 kilometers, northwest); and Modesto City-County Airport (4.4%, 88 kilometers, northeast).

Other Data

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.