Photo: Doc Searls · CC BY-SA 2.0Half Moon Bay has some of the coolest summers among U.S. towns
January nights here settle around 45°. A year here swings 24° from midwinter lows to midsummer highs. Winters are mild: January nights here are milder than in 94% of U.S. towns. Garden chairs stay out from May to October, the months with highs of 64–69°.
A year in Half Moon Bay at a glance
Each month’s typical high and low, and what it brings.
What stands out about Half Moon Bay’s climate
Compared with towns across the U.S., with Half Moon Bay’s place in California beside it.
What a year in Half Moon Bay feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Frost and day counts come from NOAA’s station at Half Moon Bay, CA, 0.4 miles from the town’s center, at about the same height.
The 2023 USDA map puts Half Moon Bay’s center in zone 10a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 30°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
About 25 inches of rain a year
December is the wettest month and July the driest. Rain falls on about 116 days a year. Snow is rare: about 0.0" in a normal year at Half Moon Bay, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Half Moon Bay
Nearly all of the work is heating: a normal year has almost no cooling days. Months averaging under 55° run from November through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Half Moon Bay, CA.
Living with Half Moon Bay’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 10a. Frost comes about 8 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 16 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Half Moon Bay from natural hazards, earthquakes are the largest share (59%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Half Moon Bay and similar climates
TownRatings has no climate map of the towns around Half Moon Bay yet.
Climates most like Half Moon Bay’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Half Moon Bay, CA | 45° | 67° | 25" | 0.0" |
| Port Angeles, WA | 37° | 69° | 28" | 0.4" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Coos Bay, OR | 40° | 66° | 61" | 0.2" |
| Nantucket, MA | 26° | 76° | 44" | 25" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
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°).
A bigger shift than in 71% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Half Moon Bay compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Half Moon Bay’s place among California’s.
Half Moon Bay weather by month
Highs, lows and precipitation from NOAA’s grid at Half Moon Bay’s center; snow, wet days and snow on the ground from Half Moon Bay, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 58° | 45° | 4.8" | 0.0" | 14 | 0 | 48° – 55° |
| February | 59° | 46° | 4.8" | 0.0" | 14 | 0 | 49° – 57° |
| March | 61° | 47° | 3.6" | 0.0" | 14 | 0 | 49° – 57° |
| April | 62° | 48° | 1.8" | 0.0" | 9 | 0 | 52° – 58° |
| May | 64° | 51° | 0.8" | 0.0" | 7 | 0 | 53° – 61° |
| June | 66° | 52° | 0.2" | 0.0" | 5 | 0 | 55° – 62° |
| July | 67° | 54° | 0.0" | 0.0" | 7 | 0 | 58° – 64° |
| August | 68° | 55° | 0.1" | 0.0" | 8 | 0 | 60° – 65° |
| September | 69° | 54° | 0.1" | 0.0" | 6 | 0 | 59° – 66° |
| October | 68° | 52° | 1.2" | 0.0" | 8 | 0 | 57° – 64° |
| November | 62° | 48° | 2.4" | 0.0" | 11 | 0 | 50° – 58° |
| December | 58° | 45° | 5.0" | 0.0" | 13 | 0 | 48° – 56° |
| Year | 63° | 50° | 24.8" | 0.0" | 116 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 49° to 57°. July is the most reliable, staying within 5°.
Where Half Moon Bay’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Half Moon Bay’s center.
- Snow: Half Moon Bay, CA (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Half Moon Bay, CA, 0.4 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Half Moon Bay’s climate
What is the weather like in Half Moon Bay?
A typical July afternoon reaches 67°, a January night drops to 45°, and snow is almost unheard of. Milder January nights than 94% of U.S. towns; cooler July afternoons than all but 50 U.S. towns.
How cold does it get in Half Moon Bay in winter?
December nights average 45°. About 5 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 48°.
How much snow does Half Moon Bay get?
About 0.0 inches in a normal winter at Half Moon Bay, CA, so most winters see none.
How hot does it get in Half Moon Bay?
July, with a typical high of 67°. 90° days are rare: none in a normal year at Half Moon Bay, CA.
When is the first and last frost in Half Moon Bay?
There is no reliable frost date: a 32° night comes in about 82% of winters at Half Moon Bay, CA, so most years bring a freeze but some pass without one.
What growing zone is Half Moon Bay in?
Zone 10a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 30°.
What is the best time of year to visit Half Moon Bay?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Half Moon Bay getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 71% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Half Moon Bay.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.