Mt Hamilton, CA Climate: Temperature & Rain by Month
Annual temperature and rainfall from NOAA NCEI's 1991–2020 normals →; comfort score computed by PlainClimate
30-year climate normals (1991-2020) from Mt Hamilton's primary NOAA station, MT HAMILTON.
The climate verdict for Mt Hamilton
A compact 28.7°F seasonal swing gives Mt Hamilton, California a steadier-than-extreme annual shape. NOAA reports an annual average of 55°F. It scores 78/100 for climate comfort (good), putting it in the top third of station-mapped location scores and exceeding 72% of them.
- 55°F
- annual average temperature (NOAA normal)
- 78/100
- comfort score, above 72% of station-mapped location scores
- 27.3"
- annual precipitation · 18" snow
- 199 days
- growing season, frost-free days
Mt Hamilton: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00045933 · Mt Hamilton, CA 55°F mean · 27.3" precip
TEMP-MILD · RANK-UPPER · PHOTO-FINISH · PRCP-MID · SWING-NARROW · COMF-TOP · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-MILD 55°F
- RANK-UPPER #4,185
- PHOTO-FINISH ≈ Fletcher
- PRCP-MID 27.3"
- SWING-NARROW 29°F
- COMF-TOP 78/100
- LOAD-HEAT 4,386 HDD
- STN-1 USC00045933
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Fletcher, NC (+ 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.
- Mt Hamilton (this station) 55°F
- Cold Pleasant Valley, AZ 55°F
- Hot Cherokee, NC 55°F
- Near Fletcher, NC 55°F
- Near Robbinsville Ag, NC 55°F
Climate Living Index · Mt Hamilton
Mt Hamilton: 73/100 · grade B
Mt Hamilton publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Mt Hamilton, not an official NOAA rating. Rankings still use Comfort Score 78/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Normal heat + freeze calendar | 0 calendar days | 100/100 · A |
| Precipitation balance | 27.3 in · 7.7 from 35 in | 73/100 · B |
| Frost-free season | 199 days/year | 64/100 · C |
| Annual temperature balance | 55.1°F · 12.4° from 67.5°F | 60/100 · C |
| Snowfall burden | 18.1 inches/year | 51/100 · D |
Mt Hamilton · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Mt Hamilton is a temperate Köppen climate: Csa
Coldest-month mean 43.2°F and warmest-month mean 71.9°F place this station in temperate, dry-summer, hot summer climates (Csa). Class Csa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: temperate, specifically temperate, dry-summer, hot summer.
- Köppen code
- Csa
- Group
- Temperate
- Warmest month
- 71.9°F
- Coldest month
- 43.2°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 Mt Hamilton sits across the climate record
Three NOAA fields for Mt Hamilton's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 61st percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 37th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Narrower than 92%
- Warmest-to-coldest month gap for Mt Hamilton is compact versus 6,861 complete station-years.
How Mt Hamilton compares across U.S. station-mapped locations
Mt Hamilton's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
78 Top 28% score exceeds 72% 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%). This entry sits in this band.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Mt Hamilton's measured station temperature trend
MethodologyAcross 52 complete annual observations from 1954 to 2025, MT HAMILTON warmed at a fitted rate of 0.19°C per decade. The line shows the fitted change relative to its first year, not raw year-to-year temperatures or a forecast.
- Mt Hamilton primary station fitted change +0.19 °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 | 50°F (10°C) | 39°F (4°C) | 44°F (7°C) | 5.0" | 4.2" | 7.9 | 0.0 |
| February | 49°F (9°C) | 38°F (3°C) | 43°F (6°C) | 4.8" | 5.3" | 8.4 | 0.0 |
| March | 51°F (11°C) | 39°F (4°C) | 45°F (7°C) | 4.4" | 3.8" | 8.2 | 0.0 |
| April | 55°F (13°C) | 41°F (5°C) | 48°F (9°C) | 2.2" | 1.8" | 6.6 | 0.0 |
| May | 62°F (17°C) | 47°F (9°C) | 55°F (13°C) | 1.3" | 0.0" | 1.5 | 0.0 |
| June | 71°F (22°C) | 56°F (13°C) | 64°F (18°C) | 0.3" | 0.0" | 0.0 | 0.3 |
| July | 79°F (26°C) | 65°F (18°C) | 72°F (22°C) | 0.0" | 0.0" | 0.0 | 1.2 |
| August | 79°F (26°C) | 65°F (18°C) | 72°F (22°C) | 0.1" | 0.0" | 0.0 | 1.1 |
| September | 75°F (24°C) | 60°F (16°C) | 67°F (20°C) | 0.2" | 0.0" | 0.0 | 0.2 |
| October | 66°F (19°C) | 52°F (11°C) | 59°F (15°C) | 1.3" | 0.0" | 0.2 | 0.0 |
| November | 55°F (13°C) | 43°F (6°C) | 49°F (10°C) | 3.0" | 0.9" | 3.5 | 0.0 |
| December | 49°F (9°C) | 38°F (3°C) | 43°F (6°C) | 4.7" | 2.1" | 8.6 | 0.0 |
The year, day by day
The calendar barely moves in Mt Hamilton: no date carries a normal high of 90°F or a normal low at freezing. The year runs between 38°F near December 12 and 80°F near July 21.
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 38°F around December 12.
Where the wet dates fall
The likeliest wet date is February 19, when 42% of years recorded at least a hundredth of an inch. The driest is July 19 at 1%. Summed across the calendar, that is about 78 wet dates a year.
The widest day
June 9 carries the biggest normal gap between afternoon and dawn, 16°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Mt Hamilton.
Where Mt Hamilton Stands Nationally
Among the steadiest day-night climates ranked: even the widest normal daily swing holds to roughly 16°F.
Mt Hamilton 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
Snow: 4.2"
12.1 days with precipitation
Snow: 5.3"
11.9 days with precipitation
Snow: 3.8"
11.2 days with precipitation
Snow: 1.8"
8.4 days with precipitation
5.5 days with precipitation
2.0 days with precipitation
0.1 days with precipitation
0.5 days with precipitation
1.6 days with precipitation
4.3 days with precipitation
Snow: 0.9"
8.5 days with precipitation
Snow: 2.1"
12.1 days with precipitation
Mt Hamilton's wet season runs through the cold months
December, January and February carry 53% of the year's precipitation here, while June through August contribute 1%. 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 28.7°F seasonal spread.
- Wettest month
- January, 5.0"
- Driest month
- July, 0.0"
- Wettest three months
- January, February, December (53% 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 Mt Hamilton's precipitation splits across the calendar
About 78 days a year record measurable precipitation here, carrying 27.3" between them, or roughly 0.35 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.
Winter brings real snow to Mt Hamilton
Mt Hamilton averages 18.1 inches of snowfall a year, with February the snowiest month on the normals, spread across roughly 11 days that record measurable snow. That is depth accumulating on the ground, which is why it can exceed the annual precipitation figure: precipitation counts the liquid the snow melts down to, and fresh snow is mostly air.
- Annual snowfall: 18.1 inches of depth.
- Days recording measurable snow: about 11 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 7% of the year's precipitation.
NOAA 1991-2020 normals. The ten-to-one ratio is a convention, not a measurement: real ratios vary with temperature, so treat the share as an order of magnitude rather than an exact split.
Frost Dates & Growing Season
First Fall Freeze
November 18
50% probability date
Last Spring Freeze
May 3
50% probability date
Growing Season
199 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
4,386
Higher = more heating needed
Cooling Degree Days
797
Higher = more cooling needed
Warmest Month
July
Coldest Month
February
Nationwide similar cities
Other rankable U.S. places outside CA closest to Mt Hamilton 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).
- Atlantic City, NJ 55°F · 0.0°F off
- Bluff, UT 55°F · 0.0°F off
- Mound City, KS 55°F · 0.0°F off
- Nashville, IL 55°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (27.3" here), excluding temperature-peer places.
- Great Bend, KS 27.3" · 0.0" off
- Big Falls, MN 27.3" · 0.0" off
- Fairmont, NE 27.3" · 0.0" off
- Milan, MN 27.4" · 0.1" off
Snow and freeze rhythm
When cold and snow define Mt Hamilton
heating led · moderate · low swing
Heating is the larger measured load in Mt Hamilton, at 4,386 degree days versus 797 for cooling. Unlike a strongly continental record, however, its 28.7°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
Mt Hamilton's frost-free season lasts about 199 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Mt Hamilton coldest normal
February
The coldest month still averages 43°F (6°C), above freezing, so this calendar has no hard winter.
-
2. Mt Hamilton typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Mt Hamilton snow peak
February
Mt Hamilton averages 18.1 inches of snow a year, with February the snowiest month on the normals.
Questions about Mt Hamilton's climate
How much snow does Mt Hamilton get? ▼
How much energy does heating and cooling require in Mt Hamilton? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Mt Hamilton's primary station: MT HAMILTON (USC00045933). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Mt Hamilton; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Mt Hamilton 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.