Average Weather in August in Walnut Creek California, United States
Daily high temperatures are around 83°F, rarely falling below 74°F or exceeding 93°F.
Daily low temperatures are around 57°F, rarely falling below 54°F or exceeding 61°F.
For reference, on July 28, the hottest day of the year, temperatures in Walnut Creek typically range from 58°F to 83°F, while on December 31, the coldest day of the year, they range from 40°F to 55°F.
Average High and Low Temperature in August
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
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 month of August in Walnut Creek experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 10% throughout the month.
The clearest day of the month is August 8, with clear, mostly clear, or partly cloudy conditions 91% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 57%, while on July 20, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.
Cloud Cover Categories in August
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during August in Walnut Creek is essentially constant, remaining about 0.0 inches throughout, and rarely exceeding 0.2 inches or falling below -0.0 inches.
Average Monthly Rainfall in August
Over the course of August in Walnut Creek, 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, 4 minutes, implying an average daily decrease of 2 minutes, 8 seconds, and weekly decrease of 14 minutes, 58 seconds.
The shortest day of the month is August 31, with 13 hours, 1 minute of daylight and the longest day is August 1, with 14 hours, 5 minutes of daylight.
Hours of Daylight and Twilight in August
The earliest sunrise of the month in Walnut Creek is 6:11 AM on August 1 and the latest sunrise is 26 minutes later at 6:37 AM on August 31.
The latest sunset is 8:16 PM on August 1 and the earliest sunset is 38 minutes earlier at 7:38 PM on August 31.
Daylight saving time is observed in Walnut Creek during 2021, 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 5:46 AM and sets 14 hours, 48 minutes later, at 8:34 PM, while on December 21, the shortest day of the year, it rises at 7:20 AM and sets 9 hours, 32 minutes later, at 4:52 PM.
Sunrise & Sunset with Twilight in August
The figure below presents a compact representation of key lunar data for August 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in August
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 Walnut Creek is essentially constant during August, remaining around 0% throughout.
For reference, on May 10, 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
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 Walnut Creek is gradually decreasing during August, decreasing from 9.5 miles per hour to 8.7 miles per hour over the course of the month.
For reference, on June 22, the windiest day of the year, the daily average wind speed is 9.9 miles per hour, while on November 1, the calmest day of the year, the daily average wind speed is 6.7 miles per hour.
Average Wind Speed in August
The hourly average wind direction in Walnut Creek throughout August is predominantly from the west, with a peak proportion of 94% on August 1.
Wind Direction in August
Walnut Creek 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 Walnut Creek is essentially constant during August, remaining around 57°F throughout.
Average Water Temperature in August
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
While it does not do so every year, freezing temperatures are seen in Walnut Creek over some winters. The day least likely to be in the growing season is January 2, with a 55% chance.
Time Spent in Various Temperature Bands and the Growing Season in August
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
The average accumulated growing degree days in Walnut Creek are rapidly increasing during August, increasing by 535°F, from 1,964°F to 2,498°F, over the course of the month.
Growing Degree Days in August
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 Walnut Creek is decreasing during August, falling by 1.1 kWh, from 8.0 kWh to 6.9 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in August
For the purposes of this report, the geographical coordinates of Walnut Creek are 37.906 deg latitude, -122.065 deg longitude, and 164 ft elevation.
The topography within 2 miles of Walnut Creek contains significant variations in elevation, with a maximum elevation change of 692 feet and an average elevation above sea level of 217 feet. Within 10 miles contains significant variations in elevation (3,802 feet). Within 50 miles also contains extreme variations in elevation (4,324 feet).
The area within 2 miles of Walnut Creek is covered by artificial surfaces (98%), within 10 miles by grassland (36%) and artificial surfaces (30%), and within 50 miles by grassland (22%) and cropland (22%).
This report illustrates the typical weather in Walnut Creek, 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 Walnut Creek.
For each station, the records are corrected for the elevation difference between that station and Walnut Creek 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 Walnut Creek is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Walnut Creek and a given station.
The stations contributing to this reconstruction are: Buchanan Field Airport (70%, 10 kilometers, north); Oakland International Airport (18%, 25 kilometers, southwest); and Livermore Municipal Airport (12%, 32 kilometers, southeast).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , 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 airports 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.