San Francisco weather in December
In December, San Francisco sees average daytime highs of 24°C and overnight lows near 17°C, with 72 mm of rain across 10.8 wet days and about 11.4 hours of daylight. It is the 10th-warmest and 8th-wettest month of the year here.
Day-to-day highs hold fairly steady near 24°C through the month. The sky is clear or mostly clear about 30% of the time in December, and the air most often feels humid.
Daylight stretches from about 11 h 30 min at the start of December to 11 h 24 min by month's end. Set against the rest of the year, December is San Francisco's 4th-clearest and 3rd-windiest month. For the whole year in context, see San Francisco's year-round climate.
- Daytime high
- 24°
- 10th warmest
- Overnight low
- 17°
- 4th coldest
- Rainfall
- 72 mm
- 10.8 wet days
- Daylight
- 11 h 24 min
- 5:50 AM – 5:15 PM
- Cloud cover
- 57%
- 4th clearest
- Wind
- 8 km/h
- 3rd windiest
- Solar energy
- 4.24 kWh/m²
- Travel score
- 6.9
- out of 10
Temperature in December
Day-to-day highs hold fairly steady near 24°C through the month.
A typical December day in San Francisco reaches about 24°C in the afternoon and slips back to 17°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 22°C and 26°C. Set against its neighbours, December runs on par with November and on par with January.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 |
| Avg low (°C) | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| 1 | 24 | 17 |
| 2 | 24 | 17 |
| 3 | 24 | 17 |
| 4 | 24 | 17 |
| 5 | 24 | 17 |
| 6 | 24 | 17 |
| 7 | 24 | 17 |
| 8 | 24 | 17 |
| 9 | 24 | 17 |
| 10 | 24 | 17 |
| 11 | 24 | 17 |
| 12 | 24 | 17 |
| 13 | 24 | 17 |
| 14 | 24 | 17 |
| 15 | 24 | 17 |
| 16 | 24 | 17 |
| 17 | 24 | 17 |
| 18 | 24 | 17 |
| 19 | 24 | 17 |
| 20 | 24 | 17 |
| 21 | 24 | 17 |
| 22 | 24 | 17 |
| 23 | 24 | 17 |
| 24 | 24 | 17 |
| 25 | 24 | 17 |
| 26 | 24 | 17 |
| 27 | 24 | 17 |
| 28 | 24 | 17 |
| 29 | 24 | 17 |
| 30 | 24 | 17 |
| 31 | 24 | 17 |
San Francisco weather by month
How December compares with the rest of the year at a glance. December is the 10th-warmest and 8th-wettest month here — the current month is highlighted below.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 25° / 16° | 29 | 5.8 | 11.5 | 7.8 |
| Feb | 25° / 16° | 20 | 4.1 | 11.7 | 8.0 |
| Mar | 26° / 17° | 20 | 5.2 | 11.9 | 7.5 |
| Apr | 27° / 17° | 62 | 11.2 | 12.2 | 6.2 |
| May | 25° / 18° | 333 | 24.7 | 12.5 | 4.2 |
| Jun | 25° / 18° | 390 | 27.3 | 12.6 | 3.8 |
| Jul | 24° / 18° | 267 | 25 | 12.5 | 4.3 |
| Aug | 25° / 18° | 352 | 26.4 | 12.3 | 4.0 |
| Sep | 24° / 17° | 424 | 28.3 | 12.1 | 3.7 |
| Oct | 24° / 17° | 444 | 28.8 | 11.8 | 3.8 |
| Nov | 24° / 17° | 224 | 21.5 | 11.5 | 4.8 |
| Dec | 24° / 17° | 72 | 10.8 | 11.4 | 6.9 |
Cloud cover in December
The sky is clear or mostly clear about 30% of the time in December.
Beyond those clear spells, partly cloudy skies cover about 24% of December, with mostly cloudy or overcast conditions the remaining 46%. Skies tend to open up as the month goes on.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 36 | 39 | 39 | 41 | 41 | 42 | 44 | 44 | 45 | 47 | 47 | 48 | 50 | 51 | 52 | 53 | 55 | 56 | 58 | 59 | 60 | 63 | 64 | 65 | 66 | 67 | 67 | 68 | 69 | 69 | 70 |
| Cloudier (%) | 64 | 61 | 61 | 59 | 59 | 58 | 56 | 56 | 55 | 53 | 53 | 52 | 50 | 49 | 48 | 47 | 45 | 44 | 42 | 41 | 40 | 37 | 36 | 35 | 34 | 33 | 33 | 32 | 31 | 31 | 30 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| 1 | 36 | 64 |
| 2 | 39 | 61 |
| 3 | 39 | 61 |
| 4 | 41 | 59 |
| 5 | 41 | 59 |
| 6 | 42 | 58 |
| 7 | 44 | 56 |
| 8 | 44 | 56 |
| 9 | 45 | 55 |
| 10 | 47 | 53 |
| 11 | 47 | 53 |
| 12 | 48 | 52 |
| 13 | 50 | 50 |
| 14 | 51 | 49 |
| 15 | 52 | 48 |
| 16 | 53 | 47 |
| 17 | 55 | 45 |
| 18 | 56 | 44 |
| 19 | 58 | 42 |
| 20 | 59 | 41 |
| 21 | 60 | 40 |
| 22 | 63 | 37 |
| 23 | 64 | 36 |
| 24 | 65 | 35 |
| 25 | 66 | 34 |
| 26 | 67 | 33 |
| 27 | 67 | 33 |
| 28 | 68 | 32 |
| 29 | 69 | 31 |
| 30 | 69 | 31 |
| 31 | 70 | 30 |
Chance of precipitation in December
San Francisco gets around 72 mm of rain over 10.8 wet days in December. The line is the day-by-day chance of measurable precipitation.
Day to day, the chance of measurable rain averages around 36% and peaks near 52% on the wettest days. The odds ease toward the end of the month.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain chance (%) | 52 | 51 | 49 | 48 | 46 | 45 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 34 | 33 | 32 | 31 | 31 | 30 | 29 | 28 | 28 | 27 | 26 | 26 | 25 | 25 | 24 |
| Rain chance (%) | |
|---|---|
| 1 | 52 |
| 2 | 51 |
| 3 | 49 |
| 4 | 48 |
| 5 | 46 |
| 6 | 45 |
| 7 | 43 |
| 8 | 42 |
| 9 | 41 |
| 10 | 40 |
| 11 | 39 |
| 12 | 38 |
| 13 | 37 |
| 14 | 36 |
| 15 | 35 |
| 16 | 34 |
| 17 | 34 |
| 18 | 33 |
| 19 | 32 |
| 20 | 31 |
| 21 | 31 |
| 22 | 30 |
| 23 | 29 |
| 24 | 28 |
| 25 | 28 |
| 26 | 27 |
| 27 | 26 |
| 28 | 26 |
| 29 | 25 |
| 30 | 25 |
| 31 | 24 |
Humidity in December
Most of December feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.
By dew point, December lands in the humid band about 58% of days. It rarely turns muggy — the humid and sticky bands barely register.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 3 |
| Comfortable (%) | 18 | 19 | 21 | 22 | 23 | 24 | 26 | 27 | 28 | 29 | 30 | 32 | 33 | 35 | 36 | 37 | 39 | 40 | 42 | 43 | 44 | 45 | 47 | 48 | 49 | 51 | 52 | 53 | 54 | 56 | 56 |
| Humid (%) | 70 | 70 | 69 | 69 | 69 | 69 | 68 | 67 | 66 | 66 | 66 | 64 | 64 | 62 | 61 | 60 | 59 | 58 | 55 | 54 | 53 | 52 | 51 | 50 | 48 | 47 | 46 | 45 | 44 | 42 | 41 |
| Muggy (%) | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 5 | 4 | 3 | 3 | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | |
|---|---|---|---|---|
| 1 | 0 | 18 | 70 | 12 |
| 2 | 0 | 19 | 70 | 11 |
| 3 | 0 | 21 | 69 | 10 |
| 4 | 0 | 22 | 69 | 9 |
| 5 | 0 | 23 | 69 | 8 |
| 6 | 0 | 24 | 69 | 7 |
| 7 | 0 | 26 | 68 | 6 |
| 8 | 1 | 27 | 67 | 5 |
| 9 | 1 | 28 | 66 | 5 |
| 10 | 1 | 29 | 66 | 4 |
| 11 | 1 | 30 | 66 | 3 |
| 12 | 1 | 32 | 64 | 3 |
| 13 | 1 | 33 | 64 | 2 |
| 14 | 1 | 35 | 62 | 2 |
| 15 | 1 | 36 | 61 | 2 |
| 16 | 1 | 37 | 60 | 2 |
| 17 | 1 | 39 | 59 | 1 |
| 18 | 1 | 40 | 58 | 1 |
| 19 | 2 | 42 | 55 | 1 |
| 20 | 2 | 43 | 54 | 1 |
| 21 | 2 | 44 | 53 | 1 |
| 22 | 2 | 45 | 52 | 1 |
| 23 | 2 | 47 | 51 | 0 |
| 24 | 2 | 48 | 50 | 0 |
| 25 | 2 | 49 | 48 | 0 |
| 26 | 2 | 51 | 47 | 0 |
| 27 | 2 | 52 | 46 | 0 |
| 28 | 2 | 53 | 45 | 0 |
| 29 | 2 | 54 | 44 | 0 |
| 30 | 2 | 56 | 42 | 0 |
| 31 | 3 | 56 | 41 | 0 |
Wind in December
Winds average 8 km/h in December.
Across December, daily wind ranges from about 7 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 7 | 7 | 7 | 7 | 7 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| 1 | 7 | calm |
| 2 | 7 | calm |
| 3 | 7 | calm |
| 4 | 7 | calm |
| 5 | 7 | calm |
| 6 | 8 | calm |
| 7 | 8 | calm |
| 8 | 8 | calm |
| 9 | 8 | calm |
| 10 | 8 | calm |
| 11 | 8 | calm |
| 12 | 8 | calm |
| 13 | 8 | calm |
| 14 | 8 | calm |
| 15 | 8 | calm |
| 16 | 8 | calm |
| 17 | 8 | calm |
| 18 | 8 | calm |
| 19 | 8 | calm |
| 20 | 8 | calm |
| 21 | 8 | calm |
| 22 | 8 | calm |
| 23 | 8 | calm |
| 24 | 8 | calm |
| 25 | 9 | calm |
| 26 | 9 | calm |
| 27 | 9 | calm |
| 28 | 9 | calm |
| 29 | 9 | calm |
| 30 | 9 | calm |
| 31 | 9 | calm |
Sunrise & sunset in December
Daylight runs from about 11 h 30 min at the start of December to 11 h 24 min by month's end. The lit band spans sunrise to sunset each day.
Days shrink by about 6 minutes over December. Sunrise moves from 5:43 AM to 5:57 AM, and sunset from 5:10 PM to 5:22 PM.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 11.5 | 11.5 | 11.5 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 | 11.4 |
| Sunrise (AM) | 5:43 | 5:43 | 5:44 | 5:44 | 5:45 | 5:45 | 5:46 | 5:46 | 5:47 | 5:47 | 5:48 | 5:48 | 5:49 | 5:49 | 5:50 | 5:50 | 5:51 | 5:51 | 5:52 | 5:52 | 5:53 | 5:53 | 5:53 | 5:54 | 5:54 | 5:55 | 5:55 | 5:56 | 5:56 | 5:57 | 5:57 |
| Sunset (PM) | 5:10 | 5:10 | 5:11 | 5:11 | 5:11 | 5:11 | 5:12 | 5:12 | 5:12 | 5:13 | 5:13 | 5:14 | 5:14 | 5:14 | 5:15 | 5:15 | 5:16 | 5:16 | 5:17 | 5:17 | 5:17 | 5:18 | 5:18 | 5:19 | 5:19 | 5:20 | 5:20 | 5:21 | 5:21 | 5:22 | 5:22 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| 1 | 11.5 | 5:43 | 5:10 |
| 2 | 11.5 | 5:43 | 5:10 |
| 3 | 11.5 | 5:44 | 5:11 |
| 4 | 11.4 | 5:44 | 5:11 |
| 5 | 11.4 | 5:45 | 5:11 |
| 6 | 11.4 | 5:45 | 5:11 |
| 7 | 11.4 | 5:46 | 5:12 |
| 8 | 11.4 | 5:46 | 5:12 |
| 9 | 11.4 | 5:47 | 5:12 |
| 10 | 11.4 | 5:47 | 5:13 |
| 11 | 11.4 | 5:48 | 5:13 |
| 12 | 11.4 | 5:48 | 5:14 |
| 13 | 11.4 | 5:49 | 5:14 |
| 14 | 11.4 | 5:49 | 5:14 |
| 15 | 11.4 | 5:50 | 5:15 |
| 16 | 11.4 | 5:50 | 5:15 |
| 17 | 11.4 | 5:51 | 5:16 |
| 18 | 11.4 | 5:51 | 5:16 |
| 19 | 11.4 | 5:52 | 5:17 |
| 20 | 11.4 | 5:52 | 5:17 |
| 21 | 11.4 | 5:53 | 5:17 |
| 22 | 11.4 | 5:53 | 5:18 |
| 23 | 11.4 | 5:53 | 5:18 |
| 24 | 11.4 | 5:54 | 5:19 |
| 25 | 11.4 | 5:54 | 5:19 |
| 26 | 11.4 | 5:55 | 5:20 |
| 27 | 11.4 | 5:55 | 5:20 |
| 28 | 11.4 | 5:56 | 5:21 |
| 29 | 11.4 | 5:56 | 5:21 |
| 30 | 11.4 | 5:57 | 5:22 |
| 31 | 11.4 | 5:57 | 5:22 |
Solar energy in December
Average shortwave solar energy reaching the ground each day in December, about 4.24 kWh/m².
For context, solar energy here swings from a low near 3.65 kWh/m² to a high of 5.95 kWh/m² in March across the year — December's 4.24 kWh/m² falls in the middle.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 3.9 | 3.9 | 3.9 | 3.9 | 4.0 | 4.0 | 4.0 | 4.0 | 4.0 | 4.1 | 4.1 | 4.1 | 4.1 | 4.2 | 4.2 | 4.2 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 | 4.4 | 4.4 | 4.4 | 4.4 | 4.5 | 4.5 | 4.5 | 4.5 | 4.5 | 4.6 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| 1 | 3.9 | Moderate |
| 2 | 3.9 | Moderate |
| 3 | 3.9 | Moderate |
| 4 | 3.9 | Moderate |
| 5 | 4.0 | Moderate |
| 6 | 4.0 | Moderate |
| 7 | 4.0 | Bright |
| 8 | 4.0 | Bright |
| 9 | 4.0 | Bright |
| 10 | 4.1 | Bright |
| 11 | 4.1 | Bright |
| 12 | 4.1 | Bright |
| 13 | 4.1 | Bright |
| 14 | 4.2 | Bright |
| 15 | 4.2 | Bright |
| 16 | 4.2 | Bright |
| 17 | 4.3 | Bright |
| 18 | 4.3 | Bright |
| 19 | 4.3 | Bright |
| 20 | 4.3 | Bright |
| 21 | 4.3 | Bright |
| 22 | 4.4 | Bright |
| 23 | 4.4 | Bright |
| 24 | 4.4 | Bright |
| 25 | 4.4 | Bright |
| 26 | 4.5 | Bright |
| 27 | 4.5 | Bright |
| 28 | 4.5 | Bright |
| 29 | 4.5 | Bright |
| 30 | 4.5 | Bright |
| 31 | 4.6 | Bright |
Hazard calendar for San Francisco
None of San Francisco's seasonal hazards are active in December. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.
San Francisco's rainy season runs May–November, when most of the year's rain falls.
Is December a good time to visit San Francisco?
Our two travel scores rate December for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).
December is a reasonable time to visit San Francisco for sightseeing.
What to pack for San Francisco in December
From December's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In December, San Francisco sees daytime highs around 24°C and nights near 17°C. Worth packing: light clothes and rain gear. About 11 days see rain.
Sea temperature near San Francisco in December
The nearest coast averages about 28°C in December — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 56 km away) is warmest in April at about 29°C and coldest in November near 28°C.
The water stays above 20°C all year — warm enough for a swim any month.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 28 | 28 | 28 |
| Comfort | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Warm | Tropical |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 29 | Tropical |
| Feb | 29 | Tropical |
| Mar | 29 | Tropical |
| Apr | 29 | Tropical |
| May | 29 | Tropical |
| Jun | 29 | Tropical |
| Jul | 29 | Tropical |
| Aug | 29 | Tropical |
| Sep | 29 | Tropical |
| Oct | 28 | Tropical |
| Nov | 28 | Warm |
| Dec | 28 | Tropical |
UV index in San Francisco in December
Clear-sky midday UV in December peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in San Francisco peaks around March 19 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 10 (extreme).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 12 | 14 | 15 | 14 | 13 | 13 | 13 | 13 | 13 | 12 | 12 | 10 |
| Level | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 12 | Extreme |
| Feb | 14 | Extreme |
| Mar | 15 | Extreme |
| Apr | 14 | Extreme |
| May | 13 | Extreme |
| Jun | 13 | Extreme |
| Jul | 13 | Extreme |
| Aug | 13 | Extreme |
| Sep | 13 | Extreme |
| Oct | 12 | Extreme |
| Nov | 12 | Extreme |
| Dec | 10 | Extreme |
Air quality in San Francisco in December
Average fine-particle pollution (PM2.5) through the year — so you can see where December falls, not just the annual average.
Air quality in San Francisco is worst in May — around 19 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (January, 9 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 10 | 11 | 17 | 19 | 17 | 18 | 17 | 16 | 14 | 12 | 10 |
| Level | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 10 | Good |
| Mar | 11 | Good |
| Apr | 17 | Moderate |
| May | 19 | Moderate |
| Jun | 17 | Moderate |
| Jul | 18 | Moderate |
| Aug | 17 | Moderate |
| Sep | 16 | Moderate |
| Oct | 14 | Moderate |
| Nov | 12 | Good |
| Dec | 10 | Good |
Where is San Francisco?
San Francisco sits at 10.0°N, 84.1°W, 1,131 m above sea level, in Costa Rica. The nearest listed city is Heredia, 1.0 km away.
Topography around San Francisco
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of San Francisco.
Within 3 km, the terrain around San Francisco has significant variations in elevation — a maximum elevation change of 271 m around an average of 1,102 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,296 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,470 m.
The land around San Francisco is covered by artificial surfaces (68%) and trees (22%) within 3 km, trees (56%) and artificial surfaces (29%) within 16 km, and trees (70%) within 80 km.
Costa Rica travel facts
- Travel advisory
- Level 2
- Exercise Increased Caution
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 59% of US
- price level, 2025
- GDP per capita
- $19,970
- 2025
- Happiness
- 7.4 / 10
- World Happiness, 2025
- Safe drinking water
- 81%
- of population, 2024
- Homicide rate
- 17.7
- per 100k, 2023
- Road deaths
- 14.8
- per 100k/yr, 2019
- Income group
- High
- World Bank
- English
- Moderate
- EF EPI 516
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for San Francisco (9.9938°, -84.1274°, elevation 1,131 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).