Foster City Weather in December

December in Foster City brings moderate temperatures around 14°C (57°F) during the day, dropping to 6°C (43°F) at night, with the most rainfall of the year.

Rainfall in Foster City in December

This month is known for heavy rainfall, so don't forget your umbrella to stay dry. Typically, you can expect about 12 days of rain this month, with 96 mm (3.8 in) on average. When it rains this month, it tends to come down fairly heavily. Showers can be substantial even if they don't last all day.

Temperature in Foster City in December

Daytime highs in Foster City in December reach 14°C (57°F), with nights around 6°C (43°F). The difference between afternoon and evening temperatures is usually noticeable. Nights fall to 6°C (43°F), which is cold enough to feel it indoors too. A good thick duvet makes all the difference for a comfortable night's sleep. December is characterized by some of the mildest temperatures of the year.

Sunshine in Foster City in December

The month brings about 160 hours of sunlight, offering a comfortable mix of sun and overcast.

Wind Speed in Foster City in December

December has wind speeds averaging 3 m/s (6 knots). You can expect comfortable light winds that steadily move flags and feel mild throughout the day. Since this is an average, daily conditions vary from gentle winds to more active breezes.

Average water temperature in December

The water is 13°C (55°F) this month — cool enough to feel refreshing on a warm day, but cold enough that most people won't stay in for long without a wetsuit.

December in Foster City has its charm, but if you're looking for destinations with pleasant temperatures and sunny skies, our weather planner can help you explore other options in the world.

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For a detailed overview over the year and the best time to visit the United States of America, check out our Foster City's climate page.

Foster City Temperature in December

Min Temperature 6°C (43°F)  

Max Temperature 14°C (57°F)  

Water Temperature 13°C (55°F) *  

Chance of Rain 41%  

Precipitation 96 mm (3.8 in)  

Rainy days 12 days  

Humidity 78% *  

Windspeed 3 m/s (6 knots) *  

Sunshine 160 hours *  

Percentage Sunshine 54% *  

* Data from: San Francisco, the United States of America (11 KM, 7 Miles).

What to Wear in Foster City in December

The weather can be unpredictable in December, so pack clothes you can easily mix and match. You could bring jeans, other long pants, and a few t-shirts. A light jacket or light sweater will be pleasant for the cooler moments. High rain levels are expected, so pack waterproof gear and an umbrella or poncho. The water temperature sits at about 13°C (55°F), which is too chilly for most people to enjoy swimming. Leave the swimsuit at home unless you love cold water. Bring sunglasses since you'll have some sunny periods throughout the month

What To Do in Foster City in December

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

5/10

Cycling

6/10

Walking

6/10

Camping

4/10

Outdoor sports

9/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit the United States of America, check out our Foster City's climate page.

More climate data for Foster City

Temperature Rainfall Sunshine Humidity Wind Speed Water Temp

See the full Foster City climate overview or explore weather in the United States of America.