United States · 1991–2020

Best time to visit
Alta Hill.

June leads for comfortable weather in Alta Hill: typically 26.8°C by day, 11.5°C at night, with 19 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortJune

Typical high26.8°C

Typical low11.5°C

Rain in June19 mm

Comfort

June

June · September · July

84climate match

Beach

July

July · August · September

76climate match

Outdoors

May

May · October · June

85climate match

The weakest month is January, scoring 5 against June’s 84 — days reach only 12.1°C, 12° below the 24°C the score treats as ideal, and 236 mm of rain falls.

Month by month

The whole year,
without the guesswork.

The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.

Jan

512.1° / 0.6°

Feb

512.8° / 1.3°

Mar

1414.3° / 2.8°

Apr

4317° / 4.5°

May

7421.6° / 8.2°

Jun

8426.8° / 11.5°

Jul

7631.2° / 14.6°

Aug

7530.9° / 13.9°

Sep

8028° / 11.2°

Oct

7622.4° / 6.9°

Nov

3115.5° / 2.8°

Dec

511.5° / 0.4°

Monthly climate evidence for Alta Hill — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	12.1°C	0.6°C	236 mm	11.6	9 h 41	5	Strong coverage
February	12.8°C	1.3°C	228 mm	10.3	10 h 40	5	Strong coverage
March	14.3°C	2.8°C	213 mm	10.9	11 h 50	14	Strong coverage
April	17°C	4.5°C	113 mm	7.4	13 h 10	43	Strong coverage
May	21.6°C	8.2°C	64 mm	5.1	14 h 18	74	Strong coverage
June	26.8°C	11.5°C	19 mm	2	14 h 55	84	Strong coverage
July	31.2°C	14.6°C	0 mm	0	14 h 40	76	Strong coverage
August	30.9°C	13.9°C	3 mm	0.4	13 h 42	75	Strong coverage
September	28°C	11.2°C	11 mm	1.3	12 h 24	80	Strong coverage
October	22.4°C	6.9°C	63 mm	3.7	11 h 06	76	Strong coverage
November	15.5°C	2.8°C	140 mm	7.6	9 h 58	31	Strong coverage
December	11.5°C	0.4°C	266 mm	11.1	9 h 25	5	Strong coverage

What has changed

Alta Hill runs +0.7°C
on the 1961–1990 baseline.

Each bar compares the 2011–2025 daytime average for that month against the same month in 1961–1990, measured at the same station. Months where the older record is too thin to compare are left blank.

Jan

+0.7

Feb

+0.2

Mar

-0.3

Apr

+1.1

May

+0.5

Jun

+1.6

Jul

+1.4

Aug

+1.1

Sep

+0.7

Oct

+0.4

Nov

+0.5

Dec

+0.2

June daytime highs, 2011–2025. Last recorded: 29.1°C.

Records at GRASS VALLEY #2, 1966–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C25 Jan 2015	-9.4°C29 Jan 1979	160 mm2 Jan 1997	659 mm2017 · driest 3 mm in 2015	60
February	27.2°C12 Feb 1971	-12.8°C6 Feb 1989	177 mm9 Feb 2014	646 mm1986 · driest 0 mm in 2020	60
March	29.4°C20 Mar 2026	-7.2°C2 Mar 1970	125 mm13 Mar 1983	595 mm1995 · driest 1 mm in 2026	59
April	31.1°C28 Apr 1987	-3.3°C1 Apr 1976	91 mm7 Apr 2018	332 mm2026 · driest 3 mm in 2021	59
May	37.2°C29 May 1984	-2.8°C1 May 1988	92 mm16 May 1996	205 mm2005 · driest 0 mm in 2021	59
June	38.9°C19 Jun 2021	2.2°C8 Jun 1988	43 mm5 Jun 2012	70 mm1995 · driest 0 mm in 2002	59
July	42.2°C16 Jul 1972	4.4°C22 Jul 1987	67 mm9 Jul 1974	97 mm1974 · driest 0 mm in 1999	58
August	42.2°C11 Aug 1971	5.0°C30 Aug 1989	46 mm15 Aug 1976	59 mm1976 · driest 0 mm in 1987	59
September	42.2°C7 Sep 2022	1.7°C29 Sep 2007	53 mm27 Sep 1986	149 mm1986 · driest 0 mm in 1987	59
October	36.7°C3 Oct 2024	-2.8°C14 Oct 1969	230 mm25 Oct 2021	379 mm2021 · driest 0 mm in 1988	59
November	30.6°C1 Nov 1966	-7.2°C19 Nov 1977	139 mm23 Nov 1988	541 mm1973 · driest 15 mm in 1995	58
December	26.7°C16 Dec 1980	-16.1°C9 Dec 1972	178 mm31 Dec 2005	706 mm1996 · driest 0 mm in 1989	60

Typical days per month at GRASS VALLEY #2, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	15	6	<1
February	0	0	11	6	1
March	<1	0	7	7	1
April	3	0	3	4	<1
May	9	2	<1	2	0
June	21	9	0	<1	0
July	30	21	0	0	0
August	30	21	0	<1	0
September	23	12	0	<1	0
October	11	2	<1	2	0
November	1	0	7	4	<1
December	0	0	17	7	<1

The best month has moved. On the 1961–1990 numbers the strongest month here was June (scoring 83); on 2011–2025 it is May (83). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in GRASS VALLEY #2’s record sorted by what it was actually like, rather than averaged
Month	Warm & dry days	Wet days	Washouts	Week with 3+ wet days	Daytime mean has ranged
January	7%	35%	20%	46%	9.8–14.8°C
February	11%	35%	21%	47%	10.5–16.8°C
March	17%	35%	20%	44%	11.3–17.6°C
April	34%	24%	11%	27%	14.0–20.2°C
May	66%	13%	5%	12%	18.7–24.2°C
June	88%	6%	2%	3%	24.1–28.7°C
July	99%	<1%	<1%	<1%	29.0–33.1°C
August	98%	2%	<1%	<1%	29.0–32.6°C
September	91%	6%	2%	5%	25.4–29.9°C
October	68%	13%	6%	14%	19.6–25.5°C
November	23%	28%	16%	37%	12.4–18.6°C
December	5%	35%	21%	46%	9.4–14.7°C

A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.

1967Each stripe is one year’s mean temperature against the 55-year average. Warmest: 2014. Coolest: 1982.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5323465
NOAA station: USC00043573 · GRASS VALLEY #2
Station distance: 2.9 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 28 usable years
Daylight: Calculated from latitude 39.23°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Important limit: Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.

These places read the same station, so their numbers are identical — distance from GRASS VALLEY #2 is what differs

Grass Valley→Alta Sierra→Lake Wildwood→Penn Valley→Rough and Ready→Alta Vista Park→

Or put two places side by side: Alta Hill vs Grass Valley

Best time to visitAlta Hill.

June

July

May

The whole year,without the guesswork.

Alta Hill runs +0.7°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Alta Hill.

The whole year,
without the guesswork.

Alta Hill runs +0.7°C
on the 1961–1990 baseline.

Nearby, measured,
and named.