Hottest (avg)
#12 / 12
On the cooler side.
December in context
How it compares to the rest of the year in San Francisco.
Wettest (avg)
#1 / 12
The wettest month of the year.
Daylight Hours
#12 / 12
Shorter days.
Windiest (avg)
#9 / 12
Close to the yearly wind average.
Highest UV
#12 / 12
UV is gentler than usual.
Most Humid
#2 / 12
Humidity sits on the higher side.
Monthly climate breakdown
A detailed look at the typical climate conditions for December.
Thermal profile
Temperature
Typical daytime high
- Nighttime low
-
- Feels like (avg)
-
Light window
Sunshine
9.6 h
Average daylight
- UV index (max)
- 3
- Typical sun hours
- 07:17 - 16:52
Wet-day pattern
Rain & Snow
Typical rainfall
- Rainy days
- 12 days
- Cloud cover (avg)
- 60%
Air feel
Humidity & Wind
81%
Average humidity
- Wind (avg)
-
- Wind (max gusts)
-
Historical daily baseline
Daily climate explorer
Pick a day to inspect the usual conditions through December in San Francisco. Based on a 30-year historical climate baseline, not a forecast.
Primary control
Select a day
Scroll to compare daily conditions. The summary updates with your selection.
Secondary context
Monthly trend
Median daytime highs across the month, with a softer low line.
Median temperatureMedian lowTypical range
Day 15 selected for December. Temperature 13.1°C.
Historical disruption baseline
Typical disruptions in December
Based on 30 years of historical data, these are the disruption patterns most likely to affect plans in December.
Cold High impact
Cold feels-like nights Measures: Cold feels-like nights (min <=5C). Observed about 61% of days (19.0 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
19.0 days / month
- Share of days
- ~61% of days
- Upper edge
- Up to ~5°C (P95)
Why this matters
Cold feels-like nights are possible on ~19 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Rain High impact
Rain disruption Measures: Likely rain disruption days. Observed about 20% of days (6.1 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
6.1 days / month
- Share of days
- ~20% of days
- Upper edge
- Up to ~37mm (P95)
Why this matters
Rain disruption risk appears on ~6 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Washout risk Measures: Washout day risk. Observed about 19% of days (5.9 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.9 days / month
- Share of days
- ~19% of days
- Upper edge
- Up to ~38mm (P95)
Why this matters
Washout conditions are possible on ~6 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Heavy rain days Measures: Heavy rain days (>=10mm). Observed about 11% of days (3.5 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
3.5 days / month
- Share of days
- ~11% of days
- Upper edge
- Up to ~42mm (P95)
Why this matters
Heavy rain is possible on ~4 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind High impact
Strong gusts Measures: Strong gust days (>=60 km/h). Observed about 8% of days (2.4 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.4 days / month
- Share of days
- ~8% of days
- Upper edge
- Up to ~102km/h (P95)
Why this matters
Strong gusts are possible on ~2 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Wind High impact
Stormy conditions Measures: Storm-impact proxy days. Observed about 8% of days (2.4 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.4 days / month
- Share of days
- ~8% of days
- Upper edge
- Up to ~103km/h (P95)
Why this matters
Stormy conditions are possible on ~2 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Show all disruptions (18 more)
Rain High impact
Washout run Measures: Multi-day washout runs. Observed about 1.4 days/month in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.4 days / month
- Share of days
- —
- Upper edge
- Up to ~35mm (P95)
Why this matters
Multi-day washout runs are possible on ~1 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Very heavy rain Measures: Very heavy rain days (>=25mm). Observed about 3% of days (1.0 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.0 days / month
- Share of days
- ~3% of days
- Upper edge
- Up to ~55mm (P95)
Why this matters
Very heavy rain is possible on ~1 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind High impact
Severe gusts Measures: Severe gust days (>=80 km/h). Observed about 2% of days (0.6 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.6 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~117km/h (P95)
Why this matters
Severe gusts are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Visibility Moderate
Fog-likely signal Measures: Fog-likely visibility proxy. Observed about 8% of days (2.5 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.5 days / month
- Share of days
- ~8% of days
- Upper edge
- Up to ~97% (P95)
Why this matters
Fog-likely conditions are possible on ~2 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Humidity Minor
High humidity Measures: High humidity days (RH >=80%). Observed about 63% of days (19.7 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
19.7 days / month
- Share of days
- ~63% of days
- Upper edge
- Up to ~95% (P95)
Why this matters
High humidity is possible on ~20 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Cloud Minor
Cloudy days Measures: Cloudy days (cloud cover >=60%). Observed about 56% of days (17.5 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
17.5 days / month
- Share of days
- ~56% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Cloudy skies are possible on ~17 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Wet days Measures: Wet days (>=0.1mm). Observed about 41% of days (12.8 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
12.8 days / month
- Share of days
- ~41% of days
- Upper edge
- Up to ~30mm (P95)
Why this matters
Measurable rain is possible on ~13 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cloud Minor
Mostly cloudy days Measures: Mostly cloudy days (cloud cover >=80%). Observed about 38% of days (11.7 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
11.7 days / month
- Share of days
- ~38% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Mostly cloudy skies are possible on ~12 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Rainy hours Measures: Rain-hours signal (>=3h rain). Observed about 35% of days (10.9 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
10.9 days / month
- Share of days
- ~35% of days
- Upper edge
- Up to ~21h (P95)
Why this matters
Several rainy hours are possible on ~11 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain Minor
Wet most of day Measures: Wet-most-of-day signal (>=6h rain). Observed about 27% of days (8.4 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
8.4 days / month
- Share of days
- ~27% of days
- Upper edge
- Up to ~22h (P95)
Why this matters
Wet-most-of-day conditions are possible on ~8 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind Minor
Gusty days Measures: Gusty days (>=40 km/h). Observed about 27% of days (8.3 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
8.3 days / month
- Share of days
- ~27% of days
- Upper edge
- Up to ~82km/h (P95)
Why this matters
Gusty conditions are possible on ~8 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Cold Minor
Cold nights Measures: Cold nights (min <=5C). Observed about 24% of days (7.6 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
7.6 days / month
- Share of days
- ~24% of days
- Upper edge
- Up to ~5°C (P95)
Why this matters
Cold nights are possible on ~8 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Cloud Minor
Overcast days Measures: Overcast days (cloud cover >=95%). Observed about 18% of days (5.7 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.7 days / month
- Share of days
- ~18% of days
- Upper edge
- Up to ~100% (P95)
Why this matters
Overcast skies are possible on ~6 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Other Minor
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data Measures: Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data. Observed about 8% of days (2.5 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.5 days / month
- Share of days
- ~8% of days
- Upper edge
- Up to ~97 (P95)
Why this matters
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data is possible on ~2 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cold Minor
Cold days Measures: Cold days (max <=10C). Observed about 4% of days (1.4 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.4 days / month
- Share of days
- ~4% of days
- Upper edge
- Up to ~10°C (P95)
Why this matters
Cold daytime conditions are possible on ~1 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Wind Minor
Breezy days Measures: Breezy days (mean wind >=25 km/h). Observed about 2% of days (0.6 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.6 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~30km/h (P95)
Why this matters
Breezy conditions are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Cold Minor
Freezing nights Measures: Freezing nights (min <=0C). Observed about 1% of days (0.3 days/month) in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.3 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~-0°C (P95)
Why this matters
Freezing nights are possible on ~0 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cold Minor
Cold snap run Measures: Cold snap runs (>=3 cold days). Observed about 0.2 days/month in December. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.2 days / month
- Share of days
- —
- Upper edge
- Up to ~9°C (P95)
Why this matters
Cold snap runs are possible on ~0 days. Long outdoor blocks become harder to sustain, so layer up and keep a warm indoor fallback nearby.
Travel planning FAQ
Frequently asked questions
Quick answers to the weather questions you ask the most.
Is December a good time to visit San Francisco?
Typical December days in San Francisco reach highs of 13°C (55°F) with nights around 7°C (45°F). It usually feels cool by day and cold after dark. It is among the wetter months, so it is wise to have some indoor backup plans or flexible activities.
What are temperatures like in December?
In December, you can usually expect highs of 13°C (55°F) and lows near 7°C (45°F). That means cool days and cold nights, so pack layers you can add or remove.
How much does it rain in December?
Rainfall in December averages 137 mm (5.4 in) across roughly 12 days. Overall it is a quite rainy time of year, so a light rain jacket and waterproof shoes are very handy.
How many hours of daylight are there in December?
You can expect about 10 hours of daylight in December. Sunrise is typically around 07:17 and sunset near 16:52. Days are on the shorter side, so plan activities around limited daylight.
How strong is the sun in December?
UV levels are moderate (around 3); sunscreen and sunglasses are still a good idea.
Is it windy in December?
In December, average wind speeds are around 13 km/h (8 mph), with gusts on the windiest days reaching about 61 km/h (38 mph). On the ground, it is it is a notably windy place, and strong gusts are fairly common.