Simi Valley in Winter
In winter (December, January and February), Simi Valley sees average daytime highs around 63°F and overnight lows near 45°F, with 9.8 in of rain over about 17 wet days across the season. It is the coldest season of the year and the wettest season of the year.
Across winter, daytime highs hold fairly steady around 63°F. The sky is clear or mostly clear about 49% of the time across winter, and the air most often feels dry.
Winter is Simi Valley's weakest season of the year to visit on our travel score. For the whole year in context, see Simi Valley's year-round climate.
- Avg daytime high
- 63°F
- coldest season of the year
- Avg overnight low
- 45°F
- Rainfall
- 9.8 in
- 17 wet days
- Avg wind
- 4 mph
- Travel score
- 6.5
- weakest season of the year
- Months
- Dec · Jan · Feb
Temperature in Simi Valley in Winter
Across winter, daytime highs hold fairly steady around 63°F.
A typical winter day in Simi Valley reaches about 63°F and drops to 45°F overnight. The warmest of the three months is February, the coolest December.
Simi Valley weather by month
How the three winter months (December, January and February) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 63° / 45° | 3.6 | 5.6 | 10 | 6.4 |
| Feb | 64° / 45° | 3.8 | 6.4 | 10.7 | 6.4 |
| Mar | 66° / 47° | 2.6 | 5.6 | 11.7 | 7.0 |
| Apr | 70° / 50° | 0.9 | 2.9 | 12.8 | 8.0 |
| May | 73° / 55° | 0.5 | 1.8 | 13.8 | 8.7 |
| Jun | 78° / 59° | 0.1 | 0.5 | 14.2 | 9.1 |
| Jul | 83° / 64° | 0.1 | 0.5 | 14.1 | 8.1 |
| Aug | 85° / 65° | 0.0 | 0.1 | 13.3 | 7.4 |
| Sep | 83° / 62° | 0.2 | 0.6 | 12.2 | 8.2 |
| Oct | 77° / 56° | 0.8 | 2.1 | 11.1 | 8.8 |
| Nov | 70° / 49° | 0.8 | 2.6 | 10.2 | 8.1 |
| Dec | 63° / 44° | 2.3 | 4.8 | 9.8 | 6.6 |
Cloud cover in Winter
The sky is clear or mostly clear about 49% of the time across winter.
Chance of precipitation in Winter
Simi Valley gets around 9.8 in of rain over 17 wet days across winter. The line is the day-by-day chance of measurable precipitation.
Humidity in Winter
Most of winter feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Winter
Winds average 4 mph across winter.
Sunrise & sunset in Winter
Daylight runs from about 9 h 54 min in early December to 11 h 12 min by late February. The lit band spans sunrise to sunset each day.
Solar energy in Winter
Average shortwave solar energy reaching the ground each day across winter, about 3.4 kWh/m².
Is winter a good time to visit Simi Valley?
Our two travel scores rate winter for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
winter is a reasonable time to visit Simi Valley for sightseeing.
What to pack for Simi Valley in Winter
From winter's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In winter, Simi Valley sees daytime highs around 63°F and nights near 45°F. Worth packing: a warm layer. About 17 days see rain.
Sea temperature near Simi Valley in Winter
The nearest coast averages about 59°F across winter — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 22 mi away) is warmest in August at about 67°F and coldest in March near 58°F.
The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 58 | 58 | 58 | 58 | 60 | 63 | 66 | 67 | 67 | 65 | 62 | 60 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Cool | Cool | Cool | Cool | Cool | Cool | Cool | Cool |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 58 | Bracing |
| Feb | 58 | Bracing |
| Mar | 58 | Bracing |
| Apr | 58 | Bracing |
| May | 60 | Cool |
| Jun | 63 | Cool |
| Jul | 66 | Cool |
| Aug | 67 | Cool |
| Sep | 67 | Cool |
| Oct | 65 | Cool |
| Nov | 62 | Cool |
| Dec | 60 | Cool |
UV index in Simi Valley in Winter
Clear-sky midday UV across winter averages around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Simi Valley peaks around June 23 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 3 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 4 | 5 | 5 | 8 | 8 | 11 | 11 | 11 | 8 | 6 | 3 | 3 |
| Level | Moderate | Moderate | Moderate | Very high | Very high | Extreme | Extreme | Extreme | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 4 | Moderate |
| Feb | 5 | Moderate |
| Mar | 5 | Moderate |
| Apr | 8 | Very high |
| May | 8 | Very high |
| Jun | 11 | Extreme |
| Jul | 11 | Extreme |
| Aug | 11 | Extreme |
| Sep | 8 | Very high |
| Oct | 6 | High |
| Nov | 3 | Moderate |
| Dec | 3 | Moderate |
Air quality in Simi Valley in Winter
Average fine-particle pollution (PM2.5) through the year — so you can see where winter falls, not just the annual average.
Air quality in Simi Valley is worst in December — around 29 µg/m³ PM2.5 (moderate), about 2.4× the cleanest month (May, 12 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) | 18 | 17 | 17 | 15 | 12 | 14 | 25 | 26 | 24 | 18 | 23 | 29 |
| Level | Moderate | Moderate | Moderate | Moderate | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 18 | Moderate |
| Feb | 17 | Moderate |
| Mar | 17 | Moderate |
| Apr | 15 | Moderate |
| May | 12 | Good |
| Jun | 14 | Moderate |
| Jul | 25 | Moderate |
| Aug | 26 | Moderate |
| Sep | 24 | Moderate |
| Oct | 18 | Moderate |
| Nov | 23 | Moderate |
| Dec | 29 | Moderate |
Where is Simi Valley?
Simi Valley sits at 34.3°N, 118.8°W, 768 ft above sea level, in United States. The nearest listed city is Moorpark, 5.6 mi away.
Topography around Simi Valley
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Simi Valley.
Within 2 miles, the terrain around Simi Valley has only modest variations in elevation — a maximum elevation change of 656 ft around an average of 886 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,028 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 8,816 ft.
The land around Simi Valley is covered by artificial surfaces (56%) within 2 miles, grassland (39%) and shrubs (21%) within 10 miles, and water (30%) and grassland (23%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- 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 Simi Valley (34.2694°, -118.7815°, elevation 768 ft), 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.