Half Moon Bay, CA climate
Half Moon Bay has warm winters and cool summers. A typical July afternoon reaches 67°, a January night drops to 45°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Half Moon Bay feels like
Winter
Spring
Summer
Fall
Half Moon Bay 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° | 45° | 4.8" | 0 | 14 | 0 | 48° – 55° |
| February | 59° | 46° | 4.8" | 0 | 14 | 0 | 49° – 57° |
| March | 61° | 47° | 3.6" | 0 | 14 | 0 | 49° – 57° |
| April | 62° | 48° | 1.8" | 0 | 9 | 0 | 52° – 58° |
| May | 64° | 51° | 0.8" | 0 | 7 | 0 | 53° – 61° |
| June | 66° | 52° | 0.2" | 0 | 5 | 0 | 55° – 62° |
| July | 67° | 54° | 0.0" | 0 | 7 | 0 | 58° – 64° |
| August | 68° | 55° | 0.1" | 0 | 8 | 0 | 60° – 65° |
| September | 69° | 54° | 0.1" | 0 | 6 | 0 | 59° – 66° |
| October | 68° | 52° | 1.2" | 0 | 8 | 0 | 57° – 64° |
| November | 62° | 48° | 2.4" | 0 | 11 | 0 | 50° – 58° |
| December | 58° | 45° | 5.0" | 0 | 13 | 0 | 48° – 56° |
| Year | 63° | 50° | 24.8" | 0.0" | 116 | 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 Half Moon Bay
Half Moon Bay gets 25 inches of rain and melted snow a year. December is the wettest month and July the driest. Rain or snow falls on about 116 days a year.
A year-round growing season
Heating and cooling a home in Half Moon Bay
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Half Moon Bay, 100% of that work is heating and 0% is cooling, so the furnace matters far more than the air conditioner.
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 Half Moon Bay 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 Half Moon Bay averaged 1.7° warmer than the 1900s. The biggest change is in August (+2.2°). The shift is larger than in 80% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Half Moon Bay’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. March swings the most: between 1991 and 2020 its average temperature ranged from 49° to 57°. July is the most reliable, staying within 5°.
Common questions about Half Moon Bay’s climate
What is the coldest month in Half Moon Bay?
December, with a typical high of 58° and a low of 45°.
What is the hottest month in Half Moon Bay?
September, with a typical high of 69° and a low of 54°.
How much snow does Half Moon Bay get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in Half Moon Bay?
Frost is uncommon. Only 82% of years see a night at 32° or below.
What is the rainiest month in Half Moon Bay?
December, with 5.0 inches of rain and melted snow. The year totals 25 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Half Moon Bay itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Half Moon Bay, CA (1 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.