January Weather in South San Francisco, United States

Last updated: June 24, 2025

In January, the average temperature in South San Francisco, United States hovers around 11°C (52°F). Expect a minimum of 3°C (38°F) and a refreshing maximum of 21°C (70°F). With precipitation totaling 106 mm (4.2 in) over approximately 9 days, you'll want to be prepared for some rain. On top of that, the air tends to be quite humid, with an average humidity of 85%.

January Temperature in South San Francisco

In January in South San Francisco, the average temperature is 11°C (52°F). Maximums can reach 21°C (70°F), and minimums can drop as low as 3°C (38°F). This mild climate makes South San Francisco an ideal destination for travelers seeking comfortable weather during this time of year.

January Weather in South San Francisco: Daily Temperature Highs, Lows, and Averages

The chart illustrates January temperature patterns in South San Francisco, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In South San Francisco, January typically has an average temperature of 11°C (52°F), with highs reaching up to 21°C (70°F) and lows dropping to around 3°C (38°F).

Data source: Temperature data for South San Francisco generated using information from the Copernicus Climate Change Service.

January Precipitation in South San Francisco

In South San Francisco in January, the total precipitation amount is 106 mm (4.2 in), spread over the course of 9 days.

January Precipitation Trends in South San Francisco

The chart displays monthly precipitation patterns in South San Francisco, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In South San Francisco, January typically receives around 106 mm (4.2 inches) of precipitation spread over approximately 9 days.

Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

January Humidity in South San Francisco

In South San Francisco in January, humidity is 85%. With an average temperature of 11°C (52°F), this humidity feels like a damp blanket wrapping around you, making travel quite uncomfortable as the air feels heavy and can sap your energy.

January Average Humidity in South San Francisco

This chart illustrates the average monthly humidity levels in South San Francisco, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in South San Francisco is approximately 85%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in South San Francisco

In South San Francisco in January, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in South San Francisco, you can check the information here.

Maximum UV Index Levels in South San Francisco for January

The chart shows the monthly maximum UV Index (UVI) for South San Francisco in January, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In January, the maximum UV index in South San Francisco typically reaches 3, which falls under the moderate exposure category.

Data source: South San Francisco January UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How January Weather in South San Francisco Compares to Other Months

Weather in South San Francisco varies notably across the year, with each month offering distinct climate conditions. This page compares January’s weather to other months in South San Francisco, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in South San Francisco, showing how January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	11°C (52°F)	106 mm (4.2 inches)	85%	moderate
February Weather	11°C (52°F)	109 mm (4.3 inches)	82%	moderate
March Weather	12°C (53°F)	78 mm (3.1 inches)	82%	very high
April Weather	13°C (55°F)	35 mm (1.4 inches)	79%	very high
May Weather	14°C (57°F)	20 mm (0.8 inches)	83%	very high
June Weather	15°C (60°F)	3 mm (0.1 inches)	84%	extreme
July Weather	15°C (60°F)	3 mm (0.1 inches)	87%	extreme
August Weather	16°C (61°F)	2 mm (0.1 inches)	87%	very high
September Weather	17°C (63°F)	2 mm (0.1 inches)	86%	very high
October Weather	16°C (60°F)	30 mm (1.2 inches)	80%	high
November Weather	13°C (56°F)	50 mm (2.0 inches)	79%	moderate
December Weather	11°C (52°F)	95 mm (3.7 inches)	79%	moderate