Average Weather in January in South San Francisco California, United States
Daily high temperatures increase by 3°F, from 55°F to 58°F, rarely falling below 50°F or exceeding 64°F.
Daily low temperatures are around 46°F, rarely falling below 39°F or exceeding 53°F. The lowest daily average low temperature is 45°F on January 3.
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 January
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on January. 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 January
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 January in South San Francisco experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 53% throughout the month. The highest chance of overcast or mostly cloudy conditions is 54% on January 13.
The clearest day of the month is January 26, with clear, mostly clear, or partly cloudy conditions 48% 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 January
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
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 January is essentially constant, remaining around 26% throughout.
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 January
The average sliding 31-day rainfall during January in South San Francisco is essentially constant, remaining about 3.5 inches throughout, and rarely exceeding 7.4 inches or falling below 0.3 inches.
Average Monthly Rainfall in January
Over the course of January in South San Francisco, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 41 minutes, implying an average daily increase of 1 minute, 22 seconds, and weekly increase of 9 minutes, 36 seconds.
The shortest day of the month is January 1, with 9 hours, 37 minutes of daylight and the longest day is January 31, with 10 hours, 18 minutes of daylight.
Hours of Daylight and Twilight in January
The latest sunrise of the month in South San Francisco is 7:25 AM on January 5 and the earliest sunrise is 11 minutes earlier at 7:14 AM on January 31.
The earliest sunset is 5:02 PM on January 1 and the latest sunset is 30 minutes later at 5:32 PM on January 31.
Daylight saving time is observed in South San Francisco during 2018, but it neither starts nor ends during January, so the entire month is in standard 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 in January
The chance that a given day will be muggy in South San Francisco is essentially constant during January, 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 January
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in South San Francisco is essentially constant during January, remaining within 0.2 miles per hour of 8.9 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 January is 8.7 miles per hour on January 21.
Average Wind Speed in January
Wind Direction in January
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 January, remaining around 53°F throughout.
The lowest average surface water temperature during January is 53°F on January 20.
Average Water Temperature in January
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 January
The average accumulated growing degree days in South San Francisco are gradually increasing during January, increasing by 69°F, from 0°F to 70°F, over the course of the month.
Growing Degree Days in January
The average daily incident shortwave solar energy in South San Francisco is gradually increasing during January, rising by 0.6 kWh, from 2.2 kWh to 2.9 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in January
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.
Time zones for aiports and weather stations are provided by AskGeo.com .