Half Moon Bay, CA Climate: Temperature & Rain by Month
Temperature and precipitation from NOAA NCEI 1991–2020 normals →, plus PlainClimate's derived comfort score
30-year climate normals (1991-2020) from Half Moon Bay's primary NOAA station, HALF MOON BAY.
The climate verdict for Half Moon Bay
A compact 8.8°F seasonal swing gives Half Moon Bay, California a steadier-than-extreme annual shape. NOAA reports an annual average of 55°F. It scores 80/100 for climate comfort (excellent), putting it in the top third of station-mapped location scores and exceeding 76% of them.
- 55°F
- annual average temperature (NOAA normal)
- 80/100
- comfort score, above 76% of station-mapped location scores
- 26.0"
- precipitation, annual total
- 314 days
- frost-free days per growing season
Half Moon Bay: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00043714 · Half Moon Bay, CA 55°F mean · 26.0" precip
TEMP-COOL · RANK-UPPER · PHOTO-FINISH · PRCP-MID · SWING-NARROW · COMF-TOP · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 55°F
- RANK-UPPER #4,117
- PHOTO-FINISH ≈ San Gregorio
- PRCP-MID 26.0"
- SWING-NARROW 9°F
- COMF-TOP 80/100
- LOAD-HEAT 3,701 HDD
- STN-1 USC00043714
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: San Gregorio, CA ( -0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CA station list.
- Hot Mapleton, OR 56°F
- Near Scotia, CA 56°F
- Half Moon Bay (this station) 55°F
- Cold Haleakala Range…, HI 55°F
- Near San Gregorio, CA 55°F
Climate Living Index · Half Moon Bay
Half Moon Bay: 81/100 · grade B
Half Moon Bay publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Half Moon Bay, not an official NOAA rating. Rankings still use Comfort Score 80/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Frost-free season | 314 days/year | 100/100 · A |
| Normal heat + freeze calendar | 0 calendar days | 100/100 · A |
| Snowfall burden | 0.0 inches/year | 90/100 · A |
| Precipitation balance | 26.0 in · 9.0 from 35 in | 68/100 · C |
| Annual temperature balance | 54.9°F · 12.6° from 67.5°F | 59/100 · C |
Half Moon Bay · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Half Moon Bay is a temperate Köppen climate: Csb
Coldest-month mean 50.9°F and warmest-month mean 59.7°F place this station in temperate, dry-summer, warm summer climates (Csb). Class Csb is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: temperate, specifically temperate, dry-summer, warm summer.
- Köppen code
- Csb
- Group
- Temperate
- Warmest month
- 59.7°F
- Coldest month
- 50.9°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Half Moon Bay sits across the climate record
Three NOAA fields for Half Moon Bay's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 60th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 35th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Narrower than 99%
- Warmest-to-coldest month gap for Half Moon Bay is compact versus 6,861 complete station-years.
How Half Moon Bay compares across U.S. station-mapped locations
Half Moon Bay's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
80 Top 24% score exceeds 76% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). Below this entry.
- 70–80: 650 station-mapped locations (11%). Below this entry.
- 80–90: 921 station-mapped locations (15%). This entry sits in this band.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Half Moon Bay's measured station temperature trend
MethodologyAcross 54 complete annual observations from 1942 to 2025, HALF MOON BAY warmed at a fitted rate of 0.18°C per decade. The line shows the fitted change relative to its first year, not raw year-to-year temperatures or a forecast.
- Half Moon Bay primary station fitted change +0.18 °C/decade
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 59°F (15°C) | 43°F (6°C) | 51°F (11°C) | 5.1" | 0.0" | 1.0 | 0.0 |
| February | 60°F (15°C) | 43°F (6°C) | 51°F (11°C) | 4.7" | 0.0" | 1.2 | 0.0 |
| March | 60°F (16°C) | 44°F (7°C) | 52°F (11°C) | 3.7" | 0.0" | 0.4 | 0.0 |
| April | 61°F (16°C) | 45°F (7°C) | 53°F (12°C) | 1.8" | 0.0" | 0.1 | 0.0 |
| May | 62°F (17°C) | 48°F (9°C) | 55°F (13°C) | 1.0" | 0.0" | 0.0 | 0.0 |
| June | 64°F (18°C) | 50°F (10°C) | 57°F (14°C) | 0.4" | 0.0" | 0.0 | 0.0 |
| July | 65°F (18°C) | 53°F (12°C) | 59°F (15°C) | 0.1" | 0.0" | 0.0 | 0.0 |
| August | 66°F (19°C) | 54°F (12°C) | 60°F (15°C) | 0.2" | 0.0" | 0.0 | 0.0 |
| September | 66°F (19°C) | 51°F (11°C) | 59°F (15°C) | 0.2" | 0.0" | 0.0 | 0.1 |
| October | 66°F (19°C) | 48°F (9°C) | 57°F (14°C) | 1.3" | 0.0" | 0.0 | 0.4 |
| November | 63°F (17°C) | 45°F (7°C) | 54°F (12°C) | 2.4" | 0.0" | 0.5 | 0.0 |
| December | 59°F (15°C) | 43°F (6°C) | 51°F (11°C) | 5.2" | 0.0" | 1.4 | 0.0 |
The year, day by day
The calendar barely moves in Half Moon Bay: no date carries a normal high of 90°F or a normal low at freezing. The year runs between 43°F near December 13 and 67°F near September 30.
No freezing date
Not one calendar date in the 1991–2020 record carries a normal low at or below 32°F. The coldest normal low of the year is 43°F around December 13.
Where the wet dates fall
The likeliest wet date is February 26, when 49% of years recorded at least a hundredth of an inch. The driest is June 18 at 17%. Summed across the calendar, that is about 116 wet dates a year.
The widest day
October 26 carries the biggest normal gap between afternoon and dawn, 19°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Half Moon Bay.
Where Half Moon Bay Stands Nationally
Among the steadiest day-night climates ranked: even the widest normal daily swing holds to roughly 19°F.
Half Moon Bay earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall and snowfall
14.4 days with precipitation
14.0 days with precipitation
13.9 days with precipitation
8.8 days with precipitation
7.2 days with precipitation
5.0 days with precipitation
7.0 days with precipitation
7.6 days with precipitation
6.3 days with precipitation
7.7 days with precipitation
10.6 days with precipitation
13.4 days with precipitation
Half Moon Bay's wet season runs through the cold months
December, January and February carry 57% of the year's precipitation here, while June through August contribute 3%. That is the cool-season-dominant pattern of the West Coast and the higher inland West, where storm tracks swing south in winter and summer turns dry; the thermometer meanwhile shows an unusually narrow 8.8°F seasonal spread.
- Wettest month
- December, 5.2"
- Driest month
- July, 0.1"
- Wettest three months
- December, January, February (57% of the year)
Shares are computed from this station's own 1991-2020 monthly precipitation normals. A cool-season label means the December-February share reaches 35%. Where snow falls, the monthly figures above report liquid-equivalent precipitation, so a wet winter month is not necessarily a rainy one.
How Half Moon Bay's precipitation splits across the calendar
About 116 days a year record measurable precipitation here, carrying 26.0" between them, or roughly 0.22 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Half Moon Bay's record shows no measurable snowfall
This station measured snowfall across the 1991-2020 period and recorded none: the annual normal is 0.0 inches. That is a measured zero rather than missing data, which is a meaningful distinction here , most stations in the database simply do not report snow at all, and those pages say nothing about it.
A thirty-year normal of zero describes the typical year at this station. It is not a claim that snow has never fallen in the area.
Frost Dates & Growing Season
First Fall Freeze
December 17
50% probability date
Last Spring Freeze
February 6
50% probability date
Growing Season
314 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
3,701
Higher = more heating needed
Cooling Degree Days
12
Higher = more cooling needed
Warmest Month
August
Coldest Month
December
Nationwide similar cities
Other rankable U.S. places outside CA closest to Half Moon Bay on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (55°F here).
- Booneville, KY 55°F · 0.0°F off
- California, MO 55°F · 0.0°F off
- Cave Junction, OR 55°F · 0.0°F off
- Clendenin, WV 55°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (26.0" here), excluding temperature-peer places.
- Rocksprings, TX 26.0" · 0.0" off
- Orr, MN 26.0" · 0.0" off
- Winfred, SD 26.0" · 0.0" off
- Copper Harbor, MI 26.0" · 0.0" off
Data-derived climate profile
How Half Moon Bay's climate pattern fits together
heating led · moderate · low swing
Heating is the larger measured load in Half Moon Bay, at 3,701 degree days versus 12 for cooling. Unlike a strongly continental record, however, its 8.8°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
The frost-free window extends for about 314 days. That is a long calendar measure, but it is not a forecast and does not combine heat, rainfall, soil, or local elevation into a planting recommendation.
Temperature varies within a narrow 8.8°F band across the normal year. August and December mark the typical warm and cold ends of the calendar. The annual average is 55°F. Monthly rows still matter, but they refine a steady profile rather than reveal two climatic extremes.
Half Moon Bay's 26.0 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Recorded annual snowfall is negligible. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Half Moon Bay's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Half Moon Bay, not an official NOAA class or a year-ahead forecast.
Questions about Half Moon Bay's climate
How much rain does Half Moon Bay get? ▼
How much energy does heating and cooling require in Half Moon Bay? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Half Moon Bay's primary station: HALF MOON BAY (USC00043714). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 0631708). Match rule for Half Moon Bay: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Half Moon Bay comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.