Alpine, California climate: Normal weather by month, frost dates and records
Alpine's normal year runs from 42°F December nights to 89°F August afternoons, with 16.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 17.0°C, December lows of 5°C, August highs of 32°C, 408 mm of precipitation a year.
- NOAA stationAlpine
- Station IDUSC00040136
- Location32.84°N 116.78°W
- Elevation1,695 ft (517 m)
- Population (census place)15,470
On October 22, the normal high in Alpine is 77°F and the normal low 53°F, and the chance of measurable rain or snow is 9%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Alpine.
- Jan 64° 43°
- Feb 64° 42°
- Mar 67° 44°
- Apr 71° 47°
- May 74° 51°
- Jun 81° 54°
- Jul 87° 60°
- Aug 89° 62°
- Sep 86° 60°
- Oct 78° 54°
- Nov 71° 48°
- Dec 63° 42°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Alpine each month?
August is the warmest month, with normal highs of 89°F; December the coldest, with normal lows of 42°F. The most precipitation falls in February (3.65 in), the least in July (0.10 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 64°F | 43°F | 53.2°F | 3.21 | 6 | <1 | 1 | 10 h 10 min |
| February | 64°F | 42°F | 53.3°F | 3.65 | 8 | <1 | 1 | 11 h |
| March | 67°F | 44°F | 55.8°F | 2.73 | 6 | <1 | <1 | 12 h |
| April | 71°F | 47°F | 58.8°F | 1.18 | 4 | 1 | <1 | 13 h |
| May | 74°F | 51°F | 62.6°F | 0.57 | 3 | 2 | <1 | 13 h 50 min |
| June | 81°F | 54°F | 67.8°F | 0.13 | 1 | 5 | <1 | 14 h 20 min |
| July | 87°F | 60°F | 73.4°F | 0.10 | 1 | 12 | <1 | 14 h 10 min |
| August | 89°F | 62°F | 75.5°F | 0.12 | 1 | 17 | <1 | 13 h 20 min |
| September | 86°F | 60°F | 73.1°F | 0.25 | 1 | 13 | <1 | 12 h 30 min |
| October | 78°F | 54°F | 66.2°F | 0.59 | 2 | 5 | <1 | 11 h 30 min |
| November | 71°F | 48°F | 59.1°F | 1.48 | 4 | <1 | <1 | 10 h 30 min |
| December | 63°F | 42°F | 52.3°F | 2.04 | 6 | <1 | 1 | 10 h |
| Year (annual) | 75°F | 51°F | 62.6°F | 16.05 | 43 | 55 | 3 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 18°C | 6°C | 11.8°C | 82 mm |
| February | 18°C | 6°C | 11.8°C | 93 mm |
| March | 20°C | 7°C | 13.2°C | 69 mm |
| April | 22°C | 8°C | 14.9°C | 30 mm |
| May | 24°C | 10°C | 17.0°C | 14 mm |
| June | 27°C | 12°C | 19.9°C | 3 mm |
| July | 30°C | 16°C | 23.0°C | 3 mm |
| August | 32°C | 17°C | 24.2°C | 3 mm |
| September | 30°C | 16°C | 22.8°C | 6 mm |
| October | 26°C | 12°C | 19.0°C | 15 mm |
| November | 21°C | 9°C | 15.1°C | 38 mm |
| December | 17°C | 5°C | 11.3°C | 52 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00040136; 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.
When is the best weather to visit Alpine?
Normal highs sit between 65°F and 85°F in March, April, May, June, October and November. 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 USC00040136.
When is the last frost in Alpine?
In Alpine, the last spring frost (32°F) comes after February 12 in half of years and after March 20 in one year in ten; the first autumn frost comes before December 24 in half of years and before December 2 in one year in ten. A night at 32°F or colder comes at all in 90% of years here (NOAA).
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- February 121 year in 10 after March 20; 9 in 10 after December 29
- First autumn frost, half of years before
- December 241 year in 10 before December 2; 9 in 10 before February 3
NOAA puts the median frost-free season at 317 days, and the season without a hard freeze (28°F) at 365 days.
A hard freeze (28°F) comes after January 22 in half of springs and before January 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Alpine in zone 9b in ZIP code 91901. By the map's own method, the average of each year's coldest night over 1991-2020, Alpine's NOAA station is in zone 10a: the coldest night of a typical year reaches 31°F (19 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 USC00040136; 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 in Alpine?
In a normal year in Alpine, 55 days a year reach 90°F (4 of them 100°F or more), 3 nights fall to 32°F or colder and 43 days bring measurable precipitation.
- Days at 90°F or more
- 55a normal year
- Days at 100°F or more
- 4a normal year
- Nights at 32°F or colder
- 3a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 43a normal year
The highest temperature in this station's record (since 1951) is 113°F, on September 5, 2020; the lowest is 19°F, on January 13, 1963.
The wettest calendar year on that record is 1978, with 34.73 in.
Source: NOAA NCEI 1991-2020 annual normals, station USC00040136; records: ACIS (NOAA Regional Climate Centers), station USC00040136. Records use complete months only; a month missing more than three days is left out.
How sunny is Alpine?
Over a year 90% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Alpine, 5.8 kWh per square metre a day. June is the sunniest month (94%) and February the cloudiest (83%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 85% | 3.5 |
| February | 83% | 4.3 |
| March | 87% | 5.7 |
| April | 89% | 7.0 |
| May | 90% | 7.7 |
| June | 94% | 8.3 |
| July | 92% | 7.7 |
| August | 94% | 7.3 |
| September | 93% | 6.3 |
| October | 91% | 5.0 |
| November | 88% | 3.8 |
| December | 84% | 3.1 |
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 much heating and cooling does Alpine need?
A normal year in Alpine brings 2,028 heating degree days, 62% fewer than the median U.S. place (5,373), and 1,167 cooling degree days, 29% more than the median (908). Three months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,757 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 367 | 1 |
| February | 332 | 3 |
| March | 291 | 6 |
| April | 207 | 21 |
| May | 120 | 46 |
| June | 31 | 113 |
| July | 2 | 264 |
| August | 1 | 328 |
| September | 9 | 252 |
| October | 72 | 108 |
| November | 203 | 26 |
| December | 394 | 1 |
| Year (annual) | 2,028 | 1,167 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00040136. 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.
Has Alpine been warmer than normal lately?
2025 averaged 63.7°F, 1.1°F above the 1991-2020 normal of 62.6°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 63.1°F | +0.5°F | 14.27 |
| 2022 | 64.3°F | +1.7°F | 10.93 |
| 2023 | 61.8°F | −0.8°F | 26.20 |
| 2024 | 63.4°F | +0.8°F | 17.24 |
| 2025 | 63.7°F | +1.1°F | 13.52 |
Over 42 complete years from 1953 to 2025, the station's annual mean temperature rose at a fitted 5.1°F per century (+0.29°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00040136; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Alpine's climate compare?
Alpine is warmer than 137 of the other 218 places with their own NOAA record in California, and wetter than 112. Across the 7,247 U.S. stations with normals, its annual mean of 62.6°F is warmer than 82%.
In the Köppen classification computed from these normals, Alpine 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 Alpine share this climate record?
Harbison Canyon has no NOAA station with 1991-2020 normals of its 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.
- Harbison Canyon, CA4,245 people · 4 mi W
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 Alpine's climate
What is the coldest month in Alpine?
December, with a normal high of 63°F and a normal low of 42°F. The warmest is August (89°F by day, 62°F at night).
What is the rainiest month in Alpine?
February, with 3.65 in of precipitation in a normal year; the driest is July with 0.10 in.
What plant hardiness zone is Alpine in?
The USDA's 2023 map puts Alpine in zone 9b in ZIP code 91901. By the same method at Alpine's NOAA station, the coldest night of a typical year reaches 31°F (19 years, 1991-2020): zone 10a.
How late can frost come in Alpine?
In half of years the last 32°F night comes after February 12; in one year in ten it comes after March 20. Waiting until March 20 leaves about a one-in-ten chance of a later frost.
Nearby and next
- California climateThe statewide normals and every place in the state
- El Capitan Dam, CA4 miles from this station, 65.4°F a year
- El Cajon, CA9 miles from this station, 65.2°F a year
- Cuyamaca, CA16 miles from this station, 54.0°F a year
- Ramona, CA16 miles from this station, 61.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made