Mount Wilson CBS, California climate: Climate normals at a NOAA weather station
Mount Wilson CBS's normal year runs from 37°F February nights to 85°F August afternoons, with 32.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 14.7°C, February lows of 3°C, August highs of 30°C, 817 mm of precipitation a year.
- NOAA stationMount Wilson CBS
- Station IDUSC00046006
- Location34.23°N 118.07°W
- Elevation5,710 ft (1,740 m)
On October 23, the normal high in Mount Wilson CBS is 70°F and the normal low 50°F, and the chance of measurable rain or snow is 10%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Mount Wilson CBS.
- Jan 56° 38°
- Feb 55° 37°
- Mar 59° 39°
- Apr 63° 42°
- May 70° 48°
- Jun 79° 58°
- Jul 85° 64°
- Aug 85° 64°
- Sep 81° 59°
- Oct 72° 51°
- Nov 63° 43°
- Dec 55° 37°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Mount Wilson CBS each month?
August is the warmest month, with normal highs of 85°F; February the coldest, with normal lows of 37°F. The most precipitation falls in February (8.26 in), the least in August (0.01 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 56°F | 38°F | 47.1°F | 7.73 | 7 | <1 | 9 | 10 h 10 min |
| February | 55°F | 37°F | 45.7°F | 8.26 | 9 | <1 | 10 | 11 h |
| March | 59°F | 39°F | 49.0°F | 5.11 | 7 | <1 | 8 | 11 h 50 min |
| April | 63°F | 42°F | 52.4°F | 2.05 | 4 | <1 | 6 | 13 h |
| May | 70°F | 48°F | 58.9°F | 1.05 | 3 | <1 | 2 | 14 h |
| June | 79°F | 58°F | 68.0°F | 0.21 | 1 | 2 | <1 | 14 h 30 min |
| July | 85°F | 64°F | 74.4°F | 0.21 | 1 | 5 | <1 | 14 h 10 min |
| August | 85°F | 64°F | 74.5°F | 0.01 | <1 | 6 | <1 | 13 h 30 min |
| September | 81°F | 59°F | 70.0°F | 0.32 | 1 | 3 | <1 | 12 h 30 min |
| October | 72°F | 51°F | 61.5°F | 1.31 | 3 | <1 | 1 | 11 h 20 min |
| November | 63°F | 43°F | 53.1°F | 1.88 | 4 | <1 | 4 | 10 h 20 min |
| December | 55°F | 37°F | 46.0°F | 4.03 | 7 | <1 | 11 | 9 h 50 min |
| Year (annual) | 68°F | 48°F | 58.4°F | 32.17 | 46 | 16 | 50 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 13°C | 3°C | 8.4°C | 196 mm |
| February | 13°C | 3°C | 7.6°C | 210 mm |
| March | 15°C | 4°C | 9.4°C | 130 mm |
| April | 17°C | 5°C | 11.3°C | 52 mm |
| May | 21°C | 9°C | 14.9°C | 27 mm |
| June | 26°C | 14°C | 20.0°C | 5 mm |
| July | 29°C | 18°C | 23.6°C | 5 mm |
| August | 30°C | 18°C | 23.6°C | 0 mm |
| September | 27°C | 15°C | 21.1°C | 8 mm |
| October | 22°C | 11°C | 16.4°C | 33 mm |
| November | 17°C | 6°C | 11.7°C | 48 mm |
| December | 13°C | 3°C | 7.8°C | 102 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Pasadena (7 miles away), gets 0 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00046006; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
Which months are mildest at Mount Wilson CBS?
Normal highs sit between 65°F and 85°F in May, June, July, September and October. Of those, June has the fewest days with rain (1).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00046006.
When is the last frost at Mount Wilson CBS?
In Mount Wilson CBS, the last spring frost (32°F) comes after April 28 in half of years and after May 27 in one year in ten; the first autumn frost comes before November 15 in half of years and before October 18 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 281 year in 10 after May 27; 9 in 10 after March 31
- First autumn frost, half of years before
- November 151 year in 10 before October 18; 9 in 10 before December 9
NOAA puts the median frost-free season at 199 days, and the season without a hard freeze (28°F) at 240 days.
A hard freeze (28°F) comes after April 8 in half of springs and before December 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Mount Wilson CBS in zone 10a in ZIP code 91024, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 8b: the coldest night of a typical year reaches 19°F (21 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in California · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00046006; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get at Mount Wilson CBS?
In a normal year in Mount Wilson CBS, 16 days a year reach 90°F, 50 nights fall to 32°F or colder and 46 days bring measurable precipitation.
- Days at 90°F or more
- 16a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 50a normal year
- Days that stay below freezing
- 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 46a normal year
The highest temperature in this station's record (since 1948) is 102°F, on July 5, 2007; the lowest is 9°F, on January 29, 1969.
The wettest calendar year on that record is 1980, with 65.95 in; the snowiest season is 1948–49, with 82.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00046006; records: ACIS (NOAA Regional Climate Centers), station USC00046006. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Mount Wilson CBS?
Over a year 90% of the sunlight that would reach the ground under clear skies gets through the clouds at Mount Wilson CBS, 5.7 kWh per square metre a day. August is the sunniest month (97%) and February the cloudiest (82%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 83% | 3.2 |
| February | 82% | 4.0 |
| March | 85% | 5.4 |
| April | 87% | 6.7 |
| May | 89% | 7.5 |
| June | 93% | 8.1 |
| July | 95% | 7.9 |
| August | 97% | 7.5 |
| September | 95% | 6.3 |
| October | 91% | 4.8 |
| November | 88% | 3.6 |
| December | 83% | 2.9 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How many heating and cooling degree days does Mount Wilson CBS record?
A normal year at Mount Wilson CBS brings 3,459 heating degree days, 36% fewer than the median U.S. place (5,373), and 1,070 cooling degree days, 18% more than the median (908). Six months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,992 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 554 | 0 |
| February | 540 | 0 |
| March | 497 | 1 |
| April | 384 | 6 |
| May | 238 | 49 |
| June | 64 | 154 |
| July | 6 | 295 |
| August | 5 | 299 |
| September | 43 | 191 |
| October | 174 | 64 |
| November | 366 | 11 |
| December | 589 | 1 |
| Year (annual) | 3,459 | 1,070 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00046006. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Have recent years at Mount Wilson CBS been warmer than normal?
Over 33 complete years from 1949 to 2015, the station's annual mean temperature rose at a fitted 8.1°F per century (+0.45°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Mount Wilson CBS's climate compare?
Mount Wilson CBS is warmer than 67 of the 219 places with their own NOAA record in California, and wetter than 171. Across the 7,247 U.S. stations with normals, its annual mean of 58.4°F is warmer than 70%.
In the Köppen classification computed from these normals, Mount Wilson CBS is Csa: temperate, dry-summer, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Mount Wilson CBS share this climate record?
4 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Monrovia, CA37,787 people · 7 mi SE
- Duarte, CA23,493 people · 8 mi SE
- Sierra Madre, CA10,775 people · 4 mi S
- Bradbury, CA883 people · 8 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Mount Wilson CBS's climate
What is the coldest month at Mount Wilson CBS?
February, with a normal high of 55°F and a normal low of 37°F. The warmest is August (85°F by day, 64°F at night).
Does it snow at Mount Wilson CBS?
Rarely. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Pasadena (7 miles away), records 0 inches of snow in a normal year.
What is the rainiest month at Mount Wilson CBS?
February, with 8.26 in of precipitation in a normal year; the driest is August with 0.01 in.
What plant hardiness zone is Mount Wilson CBS in?
The USDA's 2023 map puts Mount Wilson CBS in zone 10a in ZIP code 91024, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 19°F (21 years, 1991-2020): zone 8b.
How late can frost come at Mount Wilson CBS?
In half of years the last 32°F night comes after April 28; in one year in ten it comes after May 27. Waiting until May 27 leaves about a one-in-ten chance of a later frost.
Nearby and next
- California climateThe statewide normals and every place in the state
- Pasadena, CA7 miles from this station, 66.0°F a year
- San Gabriel, CA11 miles from this station, 66.0°F a year
- Los Angeles, CA16 miles from this station, 65.8°F a year
- Burbank, CA17 miles from this station, 65.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made