Twitchell Dam, California climate: Climate normals at a NOAA weather station
Twitchell Dam's normal year runs from 39°F December nights to 78°F August afternoons, with 18.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 14.7°C, December lows of 4°C, August highs of 25°C, 462 mm of precipitation a year.
- NOAA stationTwitchell Dam
- Station IDUSC00049111
- Location34.99°N 120.32°W
- Elevation582 ft (177 m)
On October 23, the normal high in Twitchell Dam is 74°F and the normal low 49°F, and the chance of measurable rain or snow is 11%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Twitchell Dam.
- Jan 63° 41°
- Feb 63° 43°
- Mar 65° 44°
- Apr 68° 45°
- May 70° 48°
- Jun 75° 50°
- Jul 77° 53°
- Aug 78° 54°
- Sep 78° 52°
- Oct 75° 49°
- Nov 68° 44°
- Dec 61° 39°
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 Twitchell Dam each month?
August is the warmest month, with normal highs of 78°F; December the coldest, with normal lows of 39°F. The most precipitation falls in January (4.04 in), the least in August (0.01 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 63°F | 41°F | 51.9°F | 4.04 | 8 | <1 | 4 | 10 h |
| February | 63°F | 43°F | 52.5°F | 3.43 | 9 | <1 | 2 | 10 h 50 min |
| March | 65°F | 44°F | 54.6°F | 3.25 | 8 | <1 | 1 | 11 h 50 min |
| April | 68°F | 45°F | 56.5°F | 1.47 | 4 | 1 | 1 | 13 h |
| May | 70°F | 48°F | 59.0°F | 0.55 | 2 | 2 | <1 | 14 h |
| June | 75°F | 50°F | 62.3°F | 0.10 | 1 | 3 | <1 | 14 h 30 min |
| July | 77°F | 53°F | 65.0°F | 0.04 | <1 | 4 | <1 | 14 h 20 min |
| August | 78°F | 54°F | 65.7°F | 0.01 | 1 | 4 | <1 | 13 h 30 min |
| September | 78°F | 52°F | 64.8°F | 0.07 | 1 | 5 | <1 | 12 h 30 min |
| October | 75°F | 49°F | 62.3°F | 0.88 | 3 | 5 | <1 | 11 h 20 min |
| November | 68°F | 44°F | 56.2°F | 1.40 | 5 | 1 | 2 | 10 h 20 min |
| December | 61°F | 39°F | 50.3°F | 2.96 | 9 | <1 | 5 | 9 h 50 min |
| Year (annual) | 70°F | 47°F | 58.4°F | 18.20 | 51 | 26 | 15 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 17°C | 5°C | 11.1°C | 103 mm |
| February | 17°C | 6°C | 11.4°C | 87 mm |
| March | 18°C | 7°C | 12.6°C | 83 mm |
| April | 20°C | 7°C | 13.6°C | 37 mm |
| May | 21°C | 9°C | 15.0°C | 14 mm |
| June | 24°C | 10°C | 16.8°C | 3 mm |
| July | 25°C | 12°C | 18.3°C | 1 mm |
| August | 25°C | 12°C | 18.7°C | 0 mm |
| September | 25°C | 11°C | 18.2°C | 2 mm |
| October | 24°C | 10°C | 16.8°C | 22 mm |
| November | 20°C | 7°C | 13.4°C | 36 mm |
| December | 16°C | 4°C | 10.2°C | 75 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00049111; 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 Twitchell Dam?
Normal highs sit between 65°F and 85°F in April, May, June, July, August, September, October and November. Of those, July has the fewest days with rain (0).
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 USC00049111.
When is the last frost at Twitchell Dam?
In Twitchell Dam, the last spring frost (32°F) comes after February 4 in half of years and after March 31 in one year in ten; the first autumn frost comes before December 4 in half of years and before November 14 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
- February 41 year in 10 after March 31; 9 in 10 after December 27
- First autumn frost, half of years before
- December 41 year in 10 before November 14; 9 in 10 before December 28
NOAA puts the median frost-free season at 301 days, and the season without a hard freeze (28°F) at 353 days.
A hard freeze (28°F) comes after December 31 in half of springs and before December 17 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Twitchell Dam in zone 9b in ZIP code 93454, 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 9a: the coldest night of a typical year reaches 25°F (16 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 USC00049111; 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 Twitchell Dam?
In a normal year in Twitchell Dam, 26 days a year reach 90°F (4 of them 100°F or more), 15 nights fall to 32°F or colder and 51 days bring measurable precipitation.
- Days at 90°F or more
- 26a normal year
- Days at 100°F or more
- 4a normal year
- Nights at 32°F or colder
- 15a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 51a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00049111.
How sunny is it at Twitchell Dam?
Over a year 82% of the sunlight that would reach the ground under clear skies gets through the clouds at Twitchell Dam, 5.1 kWh per square metre a day. April is the sunniest month (86%) and July the cloudiest (79%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 83% | 3.1 |
| February | 82% | 3.9 |
| March | 83% | 5.2 |
| April | 86% | 6.4 |
| May | 84% | 7.0 |
| June | 81% | 7.0 |
| July | 79% | 6.6 |
| August | 80% | 6.1 |
| September | 83% | 5.4 |
| October | 84% | 4.3 |
| November | 86% | 3.4 |
| December | 82% | 2.7 |
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 Twitchell Dam record?
A normal year at Twitchell Dam brings 2,706 heating degree days, 50% fewer than the median U.S. place (5,373), and 314 cooling degree days, 65% fewer than the median (908). Four months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,267 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 409 | 1 |
| February | 351 | 1 |
| March | 325 | 3 |
| April | 266 | 11 |
| May | 206 | 20 |
| June | 120 | 37 |
| July | 53 | 52 |
| August | 41 | 64 |
| September | 69 | 62 |
| October | 136 | 52 |
| November | 277 | 13 |
| December | 454 | 1 |
| Year (annual) | 2,706 | 314 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00049111. 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 Twitchell Dam been warmer than normal?
2025 averaged 60.8°F, 2.4°F above the 1991-2020 normal of 58.4°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 60.2°F | +1.8°F | 14.22 |
| 2022 | 60.7°F | +2.3°F | 9.08 |
| 2023 | 59.5°F | +1.1°F | 30.50 |
| 2024 | 60.6°F | +2.2°F | 16.84 |
| 2025 | 60.8°F | +2.4°F | 19.83 |
Source: observed years: ACIS, station USC00049111. A year counts only with all twelve months complete.
How does Twitchell Dam's climate compare?
Twitchell Dam is warmer than 67 of the 219 places with their own NOAA record in California, and wetter than 125. 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, Twitchell Dam is Csb: temperate, dry-summer, warm 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 Twitchell Dam share this climate record?
2 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.
- Sisquoc, CA183 people · 9 mi S
- Garey, CA38 people · 7 mi S
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 Twitchell Dam's climate
What is the coldest month at Twitchell Dam?
December, with a normal high of 61°F and a normal low of 39°F. The warmest is August (78°F by day, 54°F at night).
Does it snow at Twitchell Dam?
Rarely: NOAA's normal is no measurable snow a year.
What is the rainiest month at Twitchell Dam?
January, with 4.04 in of precipitation in a normal year; the driest is August with 0.01 in.
What plant hardiness zone is Twitchell Dam in?
The USDA's 2023 map puts Twitchell Dam in zone 9b in ZIP code 93454, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 25°F (16 years, 1991-2020): zone 9a.
How late can frost come at Twitchell Dam?
In half of years the last 32°F night comes after February 4; in one year in ten it comes after March 31. Waiting until March 31 leaves about a one-in-ten chance of a later frost.
Nearby and next
- California climateThe statewide normals and every place in the state
- Santa Maria, CA9 miles from this station, 58.6°F a year
- Pismo Beach, CA24 miles from this station, 59.1°F a year
- Lompoc, CA24 miles from this station, 59.3°F a year
- San Luis Obispo, CA25 miles from this station, 59.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made