United States · 1991–2020

Best time to visit
Bivalve.

October leads for comfortable weather in Bivalve: typically 24.7°C by day, 8.8°C at night, with 31 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortOctober

Typical high24.7°C

Typical low8.8°C

Rain in October31 mm

Comfort

October

October · June · May

87climate match

Beach

August

August · July · September

70climate match

Outdoors

May

May · April · October

91climate match

The weakest month is December, scoring 27 against October’s 87 — days reach only 14.4°C, 10° below the 24°C the score treats as ideal, and nights drop to 3.7°C.

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

3014.4° / 3.9°

Feb

3716.5° / 4.7°

Mar

5218.3° / 5.7°

Apr

6819.9° / 6.6°

May

8322.2° / 8.7°

Jun

8625.8° / 10.4°

Jul

8327.2° / 11.5°

Aug

8327.5° / 11.7°

Sep

8127.6° / 10.9°

Oct

8724.7° / 8.8°

Nov

5818.7° / 5.7°

Dec

2714.4° / 3.7°

Monthly climate evidence for Bivalve — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 25 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	14.4°C	3.9°C	121 mm	9.6	11.7°C	9 h 47	30	Strong coverage
February	16.5°C	4.7°C	133 mm	9.2	11.9°C	10 h 43	37	Strong coverage
March	18.3°C	5.7°C	89 mm	8.8	11.9°C	11 h 50	52	Strong coverage
April	19.9°C	6.6°C	43 mm	5.4	11.3°C	13 h 08	68	Strong coverage
May	22.2°C	8.7°C	24 mm	3.1	11.4°C	14 h 13	83	Strong coverage
June	25.8°C	10.4°C	6 mm	0.9	11.8°C	14 h 48	86	Strong coverage
July	27.2°C	11.5°C	0 mm	0.1	13.1°C	14 h 34	83	Strong coverage
August	27.5°C	11.7°C	1 mm	0.2	13.9°C	13 h 38	83	Strong coverage
September	27.6°C	10.9°C	2 mm	0.6	14.1°C	12 h 23	81	Strong coverage
October	24.7°C	8.8°C	31 mm	2.7	13.7°C	11 h 08	87	Strong coverage
November	18.7°C	5.7°C	71 mm	6	12.9°C	10 h 03	58	Strong coverage
December	14.4°C	3.7°C	140 mm	10.4	12.1°C	9 h 32	27	Strong coverage

What has changed

Bivalve runs +0.2°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

+1.7

Feb

+0.3

Mar

-0.1

Apr

0.0

May

-0.3

Jun

+0.2

Jul

-0.9

Aug

-0.6

Sep

-0.1

Oct

+0.7

Nov

+0.7

Dec

+0.9

October daytime highs, 2011–2025. Last recorded: 23.1°C.

Records at PETALUMA AP, 1893–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	29.4°C8 Jan 1962	-7.8°C9 Jan 1937	103 mm10 Jan 1979	421 mm1916 · driest 1 mm in 2015	111
February	31.7°C16 Feb 1913	-7.8°C7 Feb 1989	97 mm11 Feb 1925	498 mm1998 · driest 0 mm in 2020	112
March	33.9°C17 Mar 1914	-4.4°C6 Mar 1918	94 mm9 Mar 1995	382 mm1983 · driest 0 mm in 2026	113
April	36.1°C29 Apr 1981	-4.4°C24 Apr 1971	65 mm6 Apr 2018	168 mm1926 · driest 0 mm in 1949	113
May	38.3°C29 May 1950	-2.8°C10 May 1985	57 mm21 May 1921	117 mm1925 · driest 0 mm in 1919	113
June	43.3°C2 Jun 1960	0.0°C1 Jun 1930	45 mm2 Jun 1967	59 mm2011 · driest 0 mm in 1960	112
July	43.3°C14 Jul 1972	3.9°C1 Jul 1919	23 mm8 Jul 1974	24 mm1974 · driest 0 mm in 1994	113
August	40.6°C30 Aug 1968	3.9°C5 Aug 1916	25 mm20 Aug 1997	26 mm1997 · driest 0 mm in 1973	110
September	42.8°C6 Sep 2022	-0.6°C19 Sep 1929	51 mm13 Sep 1918	72 mm1918 · driest 0 mm in 1952	111
October	41.1°C2 Oct 1980	-3.9°C30 Oct 1948	131 mm24 Oct 2021	202 mm2021 · driest 0 mm in 2002	111
November	32.8°C17 Nov 1932	-6.7°C14 Nov 1916	96 mm28 Nov 1970	247 mm1926 · driest 0 mm in 1959	111
December	27.2°C26 Dec 1967	-8.9°C14 Dec 1932	109 mm27 Dec 2004	396 mm2014 · driest 0 mm in 1989	111

Typical days per month at PETALUMA AP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)
January	<1	0	6	4
February	<1	0	3	5
March	2	<1	<1	3
April	4	<1	<1	1
May	7	2	0	<1
June	16	6	0	<1
July	21	7	0	0
August	22	7	0	0
September	19	9	0	0
October	14	4	0	1
November	2	<1	3	3
December	0	0	7	4

How often, not how much — every day in PETALUMA AP’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	4%	32%	14%	40%	12.1–16.1°C
February	14%	32%	14%	39%	14.5–18.5°C
March	29%	27%	10%	30%	16.1–20.4°C
April	45%	17%	5%	16%	18.1–21.9°C
May	67%	8%	1%	6%	20.0–24.6°C
June	92%	3%	<1%	<1%	23.6–27.6°C
July	99%	<1%	0%	0%	25.9–29.7°C
August	98%	<1%	<1%	<1%	26.1–29.3°C
September	95%	3%	<1%	2%	25.6–29.6°C
October	79%	10%	4%	9%	22.3–26.7°C
November	36%	22%	9%	28%	16.5–21.3°C
December	5%	31%	14%	39%	12.3–16.2°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.

1914Each stripe is one year’s mean temperature against the 103-year average. Warmest: 2014. Coolest: 1918.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5328888
NOAA station: USC00046826 · PETALUMA AP
Station distance: 26.6 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 28 usable years
Daylight: Calculated from latitude 38.09°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 25 km from the place centre. A sheltered bay can run warmer than the open sea it is measured from.
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 PETALUMA AP is what differs

Petaluma→Rohnert Park→Cotati→Penngrove→Inverness→Burdell→

Or put two places side by side: Bivalve vs Petaluma

Best time to visitBivalve.

October

August

May

The whole year,without the guesswork.

Bivalve runs +0.2°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Bivalve.

The whole year,
without the guesswork.

Bivalve runs +0.2°C
on the 1961–1990 baseline.

Nearby, measured,
and named.