Colony House · Photo: Los Angeles · CC BY-SA 3.0Simi Valley reaches 100° on about 36 days a year, more than 98% of U.S. towns
A typical July afternoon reaches 89°, a January night drops to 44°, and snow is almost unheard of.
A year in Simi Valley at a glance
Each month’s typical high and low, and what it brings.
What stands out about Simi Valley’s climate
Compared with towns across the U.S., with Simi Valley’s place in California beside it.
What a year in Simi Valley feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 329 frost-free days a year
In half of years the last 32° night comes by January 24 and the first by December 15. Frost and day counts come from NOAA’s station at Woodland Hills Pierce College, CA, 12 miles from the city’s center point, 260 ft lower.
The 2023 USDA map puts Simi Valley’s center in zone 10a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 33°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 17 inches of rain a year
February is the wettest month and July the driest. Rain falls on about 31 days a year. Snow is rare: about 0.0" in a normal year at Piru 2 Ese, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Simi Valley
42% of the work is heating, so air conditioning is the bigger bill. Months averaging under 55° run from December.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Woodland Hills Pierce College, CA.
Living with Simi Valley’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
329 frost-free days in zone 10a. The last frost comes by Jan 24 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Dec 15.
Months with highs of 62–84° and lows of 40° or more: January, February, March, April, May, June, October, November and December. 80 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Simi Valley from natural hazards, river flooding is the largest share (57%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Simi Valley and its neighbors
Every town next door is within a degree of Simi Valley in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Simi Valley’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Simi Valley, CA | 44° | 89° | 17" | 0.0" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Port Isabel, TX | 52° | 92° | 26" | 0.2" |
| Ashland, OR | 31° | 91° | 19" | 0.5" |
| Finley, WA | 29° | 91° | 9" | 2.0" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Simi Valley averaged 2.5° warmer than the 1900s. The biggest change is in January (+3.2°).
A bigger shift than in all but 73 U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods. In a city of 125,000 people, part of the change is the city itself: pavement and buildings hold heat (the urban heat island).
How Simi Valley compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Simi Valley’s place among California’s.
Simi Valley weather by month
Highs, lows and precipitation from NOAA’s grid at Simi Valley’s center; snow, wet days and snow on the ground from Piru 2 Ese, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 67° | 44° | 3.7" | 0.0" | 6 | 0 | 51° – 62° |
| February | 67° | 43° | 4.3" | 0.0" | 6 | 0 | 49° – 64° |
| March | 70° | 46° | 2.7" | 0.0" | 5 | 0 | 50° – 66° |
| April | 74° | 48° | 0.9" | 0.0" | 2 | 0 | 55° – 64° |
| May | 77° | 52° | 0.3" | 0.0" | 1 | 0 | 58° – 71° |
| June | 83° | 56° | 0.1" | 0.0" | 0 | 0 | 65° – 74° |
| July | 89° | 60° | 0.0" | 0.0" | 0 | 0 | 71° – 80° |
| August | 91° | 60° | 0.0" | 0.0" | 0 | 0 | 73° – 80° |
| September | 88° | 58° | 0.1" | 0.0" | 1 | 0 | 69° – 78° |
| October | 80° | 53° | 0.6" | 0.0" | 2 | 0 | 63° – 73° |
| November | 73° | 47° | 1.1" | 0.0" | 3 | 0 | 53° – 64° |
| December | 66° | 42° | 2.9" | 0.0" | 5 | 0 | 50° – 61° |
| Year | 77° | 51° | 16.5" | 0.0" | 31 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 50° to 66°. August is the most reliable, staying within 7°.
Where Simi Valley’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Simi Valley’s center.
- Snow: Piru 2 Ese, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Woodland Hills Pierce College, CA, 12 miles from the city’s center point, 260 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Simi Valley’s climate
What is the weather like in Simi Valley?
A typical July afternoon reaches 89°, a January night drops to 44°, and snow is almost unheard of. Milder January nights than 92% of U.S. towns; hotter July afternoons than 74% of U.S. towns.
How cold does it get in Simi Valley in winter?
December nights average 42°. About 11 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 50°.
How much snow does Simi Valley get?
About 0.0 inches in a normal winter at Piru 2 Ese, CA, so most winters see none.
How hot does it get in Simi Valley?
July, with a typical high of 89° and a low of 60°. About 115 days a year reach 90° and 36 reach 100° (Woodland Hills Pierce College, CA).
When is the first and last frost in Simi Valley?
In half of years the last spring frost (32°) comes by January 24 and the first fall frost by December 15, about 329 frost-free days, at Woodland Hills Pierce College, CA.
What growing zone is Simi Valley in?
Zone 10a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 33°.
What is the best time of year to visit Simi Valley?
By one simple rule (highs of 62–84° and lows of 40° or more), January, February, March, April, May, June, October, November and December. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Simi Valley getting warmer?
Yes: 1991–2020 averaged 2.5° warmer than 1901–2000 on NOAA’s grid. A bigger shift than all but 73 U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Simi Valley.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.