Average Weather in October in South San Francisco California, United States
Daily low temperatures decrease by 3°F, from 57°F to 53°F, rarely falling below 48°F or exceeding 61°F.
For reference, on September 14, the hottest day of the year, temperatures in South San Francisco typically range from 57°F to 71°F, while on January 3, the coldest day of the year, they range from 45°F to 55°F.
Average High and Low Temperature in October
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on October. 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 October
La Serena, Chile (5,725 miles away); Cilaos, Réunion (11,301 miles); and Anglesea, Australia (7,927 miles) are the far-away foreign places with temperatures most similar to South San Francisco (view comparison).
The month of October in South San Francisco experiences very rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 18% to 35%.
The clearest day of the month is October 1, with clear, mostly clear, or partly cloudy conditions 82% of the time.
For reference, on January 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 54%, 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 October
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In South San Francisco, the chance of a wet day over the course of October is very rapidly increasing, starting the month at 4% and ending it at 13%.
For reference, the year's highest daily chance of a wet day is 30% on February 21, and its lowest chance is -0% on July 24.
Probability of Precipitation in October
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 October in South San Francisco is rapidly increasing, starting the month at 0.4 inches, when it rarely exceeds 1.2 inches or falls below -0.0 inches, and ending the month at 1.5 inches, when it rarely exceeds 3.5 inches or falls below 0.1 inches.
Average Monthly Rainfall in October
Over the course of October in South San Francisco, 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, 9 minutes, implying an average daily decrease of 2 minutes, 18 seconds, and weekly decrease of 16 minutes, 6 seconds.
The shortest day of the month is October 31, with 10 hours, 38 minutes of daylight and the longest day is October 1, with 11 hours, 47 minutes of daylight.
Hours of Daylight and Twilight in October
The earliest sunrise of the month in South San Francisco is 7:05 AM on October 1 and the latest sunrise is 29 minutes later at 7:33 AM on October 31.
The latest sunset is 6:52 PM on October 1 and the earliest sunset is 40 minutes earlier at 6:12 PM on October 31.
Daylight saving time is observed in South San Francisco during 2018, but it neither starts nor ends during October, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:48 AM and sets 14 hours, 46 minutes later, at 8:34 PM, while on December 21, the shortest day of the year, it rises at 7:21 AM and sets 9 hours, 33 minutes later, at 4:54 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in October
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 South San Francisco is essentially constant during October, remaining around 0% throughout.
For reference, on August 24, 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 October
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 South San Francisco is essentially constant during October, remaining within 0.1 miles per hour of 7.6 miles per hour throughout.
For reference, on May 30, the windiest day of the year, the daily average wind speed is 10.1 miles per hour, while on October 5, the calmest day of the year, the daily average wind speed is 7.5 miles per hour.
The lowest daily average wind speed during October is 7.5 miles per hour on October 5.
Average Wind Speed in October
Wind Direction in October
South San Francisco 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 South San Francisco is essentially constant during October, remaining within 1°F of 57°F throughout.
Average Water Temperature in October
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).
Temperatures in South San Francisco are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in October
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 South San Francisco are increasing during October, increasing by 319°F, from 2,151°F to 2,470°F, over the course of the month.
Growing Degree Days in October
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 South San Francisco is rapidly decreasing during October, falling by 1.7 kWh, from 5.3 kWh to 3.6 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in October
For the purposes of this report, the geographical coordinates of South San Francisco are 37.655 deg latitude, -122.408 deg longitude, and 39 ft elevation.
The topography within 2 miles of South San Francisco contains very significant variations in elevation, with a maximum elevation change of 1,152 feet and an average elevation above sea level of 127 feet. Within 10 miles also contains very significant variations in elevation (1,909 feet). Within 50 miles contains very significant variations in elevation (4,321 feet).
The area within 2 miles of South San Francisco is covered by artificial surfaces (67%), water (15%), and grassland (11%), within 10 miles by water (52%) and artificial surfaces (31%), and within 50 miles by water (45%) and grassland (18%).
This report illustrates the typical weather in South San Francisco 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in South San Francisco.
For each station, the records are corrected for the elevation difference between that station and South San Francisco 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 South San Francisco is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between South San Francisco and a given station.
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.