St. Helena, CA climate
St. Helena has mild winters and warm summers. A typical July afternoon reaches 89°, a January night drops to 38°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in St. Helena feels like
Winter
Spring
Summer
Fall
St. Helena weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 58° | 38° | 6.6" | 0 | 13 | 0 | 44° – 54° |
| February | 62° | 40° | 6.3" | 0 | 11 | 0 | 46° – 57° |
| March | 67° | 41° | 4.5" | 0 | 10 | 0 | 47° – 61° |
| April | 71° | 44° | 1.9" | 0 | 6 | 0 | 51° – 62° |
| May | 78° | 48° | 1.0" | 0 | 3 | 0 | 56° – 70° |
| June | 85° | 52° | 0.2" | 0 | 1 | 0 | 65° – 72° |
| July | 89° | 54° | 0.0" | 0 | 0 | 0 | 69° – 75° |
| August | 89° | 54° | 0.0" | 0 | 0 | 0 | 68° – 75° |
| September | 87° | 51° | 0.1" | 0 | 1 | 0 | 66° – 72° |
| October | 79° | 47° | 1.5" | 0 | 3 | 0 | 60° – 69° |
| November | 66° | 41° | 3.2" | 0 | 8 | 0 | 46° – 58° |
| December | 57° | 37° | 6.6" | 0 | 13 | 0 | 43° – 51° |
| Year | 74° | 46° | 31.8" | 0.0" | 69 | 0 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in St. Helena
St. Helena gets 32 inches of rain and melted snow a year. December is the wettest month and July the driest. Rain or snow falls on about 69 days a year.
About 306 frost-free days a year
In half of years the last 32° night comes by February 3 and the first one by December 4. That leaves about 306 frost-free days for gardens, longer than 95% of U.S. towns.
Heating and cooling a home in St. Helena
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In St. Helena, 72% of that work is heating and 28% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How St. Helena compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in St. Helena averaged 1.6° warmer than the 1900s. The biggest change is in January (+2.5°). The shift is larger than in 73% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at St. Helena’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. May swings the most: between 1991 and 2020 its average temperature ranged from 56° to 70°. September is the most reliable, staying within 6°.
Common questions about St. Helena’s climate
What is the coldest month in St. Helena?
December, with a typical high of 57° and a low of 37°.
What is the hottest month in St. Helena?
July, with a typical high of 89° and a low of 54°. About 55 days a year reach 90°.
How much snow does St. Helena get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in St. Helena?
In half of years the first 32° night comes by December 4, and the last spring frost by February 3.
What is the rainiest month in St. Helena?
December, with 6.6 inches of rain and melted snow. The year totals 32 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for St. Helena itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Saint Helena, CA (1 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.