San Mateo, United States — Weather in December 2026

Climate Overview

San Mateo, United States in December has mild conditions, with highs averaging 14.5°C (58°F) and noticeably cooler mornings. Sea temperature stays cool at 12.7°C (55°F).

This month falls at the beginning of Winter.

Temperatures remain fairly steady throughout December, with daily highs around 15°C (59°F).

Rainfall is heaviest during the last third of the month, while the first third tends to be drier.

Expect around 7.2h of sunshine at the start of December, decreasing to 6.5h by the end.

The warmest days tend to fall around the 5th, averaging 15.5°C (60°F).

Compared to November, this month is about 3°C cooler with 3 more rainy days.

Monthly December Averages

Temperature

15°C / 8°C

Feels Like

13°C / 6°C

Rain

9 days · 98 mm

Sunshine

6.7h / day

Humidity

83% — Very Humid

Wind

12 km/h

Wind Direction

NNE (32°)

Gusts

32 km/h

Daylight

9.6 h

Cloud Cover

64%

Clear Sky Days

2.9

UV Index

2.7 — Moderate

Sea Temperature

13°C

Dew Point

9°C — Dry

Moon Phase

Waxing Crescent · 31%

Climate Charts

Daily averages based on historical data (2016–2025)

Daily Temperature

High Low

Daily Precipitation

Rainfall

Daily Sunshine

Sunshine

Daily Wind Speed

Wind Speed

Sun Position

Sunrise 07:17

Daylight 9.6h

Sunset 16:52

Compare Months

3days (18 mm) Excellent

0days (1 mm) Excellent

0days (0 mm) Excellent

0days (1 mm) Excellent

1days (3 mm) Excellent

2days (24 mm) Excellent

Month	Temp	Feels Like	Rain	Sun	Humidity	UV	Status	Details
January	15°C / 8°C	13°C / 6°C	10days (112 mm) Wet	6.9h Fair	84% Humid	3 Moderate	Fair	View Details
February	16°C / 8°C	14°C / 6°C	7days (90 mm) Good	8.5h Good	79% Humid	3.8 Moderate	Fair	View Details
March	16°C / 9°C	15°C / 7°C	12days (99 mm) Wet	9.4h Good	79% Humid	5.6 High	Good	View Details
April	18°C / 10°C	18°C / 8°C	5days (30 mm) Good	11h Excellent	77% Humid	6.9 High	Good	View Details
May	20°C / 11°C	20°C / 10°C	3days (18 mm) Excellent	12.5h Excellent	75% Muggy	7.9 Very High	Good	View Details
June	23°C / 13°C	23°C / 12°C	0days (1 mm) Excellent	13.3h Excellent	72% Muggy	8.2 Very High	Excellent	View Details
July best	23°C / 14°C	24°C / 13°C	0days (0 mm) Excellent	13.1h Excellent	74% Muggy	8.2 Very High	Excellent	View Details
August best	24°C / 15°C	25°C / 15°C	0days (1 mm) Excellent	12.3h Excellent	75% Muggy	7.6 Very High	Excellent	View Details
September best	25°C / 15°C	25°C / 15°C	1days (3 mm) Excellent	11.3h Excellent	74% Muggy	6.4 High	Excellent	View Details
October best	23°C / 14°C	22°C / 13°C	2days (24 mm) Excellent	9.6h Good	72% Muggy	5 Moderate	Excellent	View Details
November	18°C / 11°C	17°C / 9°C	6days (54 mm) Good	8.1h Good	79% Humid	3.4 Moderate	Good	View Details
December	15°C / 8°C	13°C / 6°C	9days (98 mm) Wet	6.7h Fair	83% Humid	2.7 Moderate	Fair	View Details

What to Wear

Bundle up with a warm coat, scarf, and closed-toe shoes. Thermal layers underneath give flexibility between indoors and outdoors.

A waterproof jacket or compact umbrella is recommended for occasional showers.

Packing List

Layered clothingLight jacketUmbrellaComfortable walking shoes

Frequently Asked Questions

Expand all

Is December a good time to visit San Mateo?

December is typically fair for visiting San Mateo, with average highs of 15°C (58°F) and around 9 rainy days. San Mateo, United States in December has mild conditions, with highs averaging 14.5°C (58°F) and noticeably cooler morni

Does it rain a lot in San Mateo in December?

San Mateo typically sees around 9 rainy days in December with 98 mm (3.9 in) of total rainfall. An umbrella should suffice.

Does it get cold at night in San Mateo in December?

Nights in San Mateo during December are cool at around 8°C (47°F). Bring a jacket or sweater for evenings.

What should I pack for San Mateo in December?

With highs of 15°C (58°F) and lows of 8°C (47°F) in December, we recommend: Layered clothing, Light jacket, Umbrella, Comfortable walking shoes. Comfortable walking shoes are essential.

Is December among the best months weather-wise in San Mateo?

December is not the most favourable month weather-wise in San Mateo. Consider visiting during months with milder temperatures or less rainfall for a better experience.

What is the UV index in San Mateo in December?

The average UV index in San Mateo during December is 3 (moderate). Sunscreen and sunglasses are recommended during midday hours.

How many hours of daylight are there in San Mateo in December?

San Mateo gets approximately 10 hours of daylight per day in December, with around 7 hours of sunshine.

Does it snow in San Mateo in December?

Snow is uncommon in San Mateo during December based on 10-year climate averages.

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