United States · 1991–2020

Best time to visit
San Ramon.

June leads for comfortable weather in San Ramon: typically 25.2°C by day, 12.2°C at night, with 7 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortJune

Typical high25.2°C

Typical low12.2°C

Rain in June7 mm

Comfort

June

June · October · September

91climate match

Beach

July

July · August · September

84climate match

Outdoors

May

May · October · April

95climate match

The weakest month is January, scoring 25 against June’s 91 — days reach only 13°C, 11° below the 24°C the score treats as ideal.

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

2513° / 4.5°

Feb

2813.5° / 4.5°

Mar

4015.2° / 5.3°

Apr

5817.5° / 6.1°

May

7820.8° / 8.8°

Jun

9125.2° / 12.2°

Jul

8328.8° / 15.5°

Aug

8328.9° / 15.2°

Sep

8727.5° / 14.4°

Oct

8922.9° / 11.1°

Nov

5416.6° / 6.9°

Dec

2512.7° / 4.2°

Monthly climate evidence for San Ramon — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	13°C	4.5°C	128 mm	9.9	9 h 49	25	Strong coverage
February	13.5°C	4.5°C	125 mm	9.7	10 h 44	28	Strong coverage
March	15.2°C	5.3°C	94 mm	8.6	11 h 50	40	Strong coverage
April	17.5°C	6.1°C	49 mm	5.5	13 h 07	58	Strong coverage
May	20.8°C	8.8°C	29 mm	3.2	14 h 11	78	Strong coverage
June	25.2°C	12.2°C	7 mm	0.9	14 h 46	91	Strong coverage
July	28.8°C	15.5°C	0 mm	0	14 h 32	83	Strong coverage
August	28.9°C	15.2°C	1 mm	0.2	13 h 37	83	Strong coverage
September	27.5°C	14.4°C	3 mm	0.6	12 h 23	87	Strong coverage
October	22.9°C	11.1°C	30 mm	2.5	11 h 09	89	Strong coverage
November	16.6°C	6.9°C	67 mm	6.2	10 h 05	54	Strong coverage
December	12.7°C	4.2°C	127 mm	9.1	9 h 34	25	Strong coverage

What has changed

San Ramon runs -1.0°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

+0.1

Feb

-0.7

Mar

-0.7

Apr

-0.4

May

-1.7

Jun

-1.0

Jul

-2.6

Aug

-1.9

Sep

-1.5

Oct

-0.9

Nov

-0.3

Dec

-0.4

June daytime highs, 2011–2025. Last recorded: 25.8°C.

Records at MT DIABLO JUNCTION, 1952–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C22 Jan 1989	-7.8°C22 Jan 1962	128 mm21 Jan 1967	533 mm2023 · driest 0 mm in 2015	74
February	26.7°C18 Feb 1977	-10.0°C6 Feb 1989	120 mm1 Feb 1963	422 mm2017 · driest 0 mm in 1964	74
March	30.0°C21 Mar 2026	-5.0°C26 Mar 1991	69 mm10 Mar 2023	290 mm2016 · driest 2 mm in 2026	73
April	35.6°C22 Apr 1987	-5.0°C20 Apr 2008	64 mm7 Apr 2018	155 mm1958 · driest 3 mm in 2021	74
May	38.9°C6 May 1987	-0.6°C1 May 1988	42 mm16 May 1996	118 mm1998 · driest 0 mm in 1992	75
June	41.7°C16 Jun 1961	1.1°C6 Jun 2000	29 mm5 Jun 2011	94 mm2011 · driest 0 mm in 1960	75
July	43.9°C15 Jul 1972	1.1°C5 Jul 1955	14 mm9 Jul 1974	14 mm1974 · driest 0 mm in 1997	73
August	41.7°C11 Aug 1971	4.4°C31 Aug 2000	16 mm19 Aug 1976	28 mm1976 · driest 0 mm in 1982	74
September	41.7°C4 Sep 1955	1.7°C20 Sep 2007	51 mm19 Sep 1959	71 mm1959 · driest 0 mm in 2008	74
October	37.8°C3 Oct 2024	-1.1°C19 Oct 1990	153 mm25 Oct 2021	271 mm1962 · driest 0 mm in 2013	72
November	32.2°C2 Nov 1966	-3.3°C30 Nov 2007	91 mm6 Nov 1994	200 mm1970 · driest 0 mm in 1959	72
December	25.0°C27 Dec 1980	-10.0°C22 Dec 1990	123 mm23 Dec 1955	391 mm1955 · driest 0 mm in 1989	74

Typical days per month at MT DIABLO JUNCTION, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)
January	0	0	4	4
February	0	0	4	4
March	<1	0	2	4
April	3	<1	2	2
May	8	2	0	1
June	16	7	0	<1
July	25	13	0	0
August	26	13	0	0
September	22	11	0	<1
October	12	3	0	1
November	2	0	2	2
December	0	0	5	4

The best month has moved. On the 1961–1990 numbers the strongest month here was October (scoring 91); on 2011–2025 it is June (93). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in MT DIABLO JUNCTION’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%	30%	12%	39%	10.6–15.1°C
February	10%	29%	13%	38%	11.5–16.6°C
March	19%	28%	10%	33%	12.1–18.0°C
April	37%	18%	6%	16%	14.6–20.6°C
May	59%	8%	2%	6%	18.0–24.1°C
June	84%	3%	<1%	<1%	22.4–29.0°C
July	97%	<1%	<1%	0%	26.6–32.4°C
August	97%	1%	<1%	<1%	26.8–31.7°C
September	92%	3%	<1%	2%	25.7–30.2°C
October	71%	9%	4%	8%	20.3–26.5°C
November	26%	21%	8%	26%	14.2–19.3°C
December	7%	28%	12%	33%	10.8–15.7°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.

1953Each stripe is one year’s mean temperature against the 68-year average. Warmest: 1959. Coolest: 2007.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5392593
NOAA station: USC00045915 · MT DIABLO JUNCTION
Station distance: 11.8 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 29 usable years
Daylight: Calculated from latitude 37.78°, 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 MT DIABLO JUNCTION is what differs

Danville→Alamo→Clayton→Blackhawk→Diablo→North Gate→

Or put two places side by side: San Ramon vs Danville

Best time to visitSan Ramon.

June

July

May

The whole year,without the guesswork.

San Ramon runs -1.0°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
San Ramon.

The whole year,
without the guesswork.

San Ramon runs -1.0°C
on the 1961–1990 baseline.

Nearby, measured,
and named.