United States · 1991–2020

Best time to visit
Fullerton.

September leads for comfortable weather in Fullerton: typically 26°C by day, 11.3°C at night, with 64 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high26°C

Typical low11.3°C

Rain in September64 mm

Comfort

September

September · May · August

80climate match

Beach

August

August · July · June

76climate match

Outdoors

October

October · September · April

79climate match

The weakest month is January, scoring 5 against September’s 80 — days reach only 1.9°C, 22° below the 24°C the score treats as ideal, and nights drop to -10.4°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

51.9° / -10.4°

Feb

54.4° / -8.5°

Mar

2411.5° / -2.7°

Apr

4917.8° / 3°

May

7223.3° / 9.5°

Jun

6928.4° / 15.4°

Jul

6530.3° / 17.6°

Aug

7229° / 16.3°

Sep

8026° / 11.3°

Oct

5818.8° / 3.9°

Nov

2210.4° / -3.2°

Dec

53.4° / -8.5°

Monthly climate evidence for Fullerton — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	1.9°C	-10.4°C	17 mm	3.6	9 h 29	5	Strong coverage
February	4.4°C	-8.5°C	20 mm	3.8	10 h 33	5	Strong coverage
March	11.5°C	-2.7°C	41 mm	5.3	11 h 48	24	Strong coverage
April	17.8°C	3°C	76 mm	6.9	13 h 16	49	Strong coverage
May	23.3°C	9.5°C	111 mm	9.2	14 h 29	72	Strong coverage
June	28.4°C	15.4°C	112 mm	8.1	15 h 09	69	Strong coverage
July	30.3°C	17.6°C	75 mm	7	14 h 53	65	Strong coverage
August	29°C	16.3°C	77 mm	6.6	13 h 50	72	Strong coverage
September	26°C	11.3°C	64 mm	5.7	12 h 25	80	Strong coverage
October	18.8°C	3.9°C	55 mm	5.7	11 h 01	58	Strong coverage
November	10.4°C	-3.2°C	31 mm	3.6	9 h 48	22	Strong coverage
December	3.4°C	-8.5°C	24 mm	3.9	9 h 12	5	Strong coverage

What has changed

Fullerton 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

+1.2

Feb

+0.1

Mar

+2.5

Apr

-0.2

May

-0.2

Jun

+0.5

Jul

-1.0

Aug

-1.2

Sep

+1.6

Oct

+0.1

Nov

+2.0

Dec

+2.4

September daytime highs, 2011–2025. Last recorded: 26.8°C.

Records at GENOA 2 W, 1893–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	23.3°C24 Jan 1981	-35.0°C12 Jan 1912	27 mm22 Jan 2018	56 mm1932 · driest 0 mm in 1986	132
February	26.7°C25 Feb 1995	-36.7°C15 Feb 2021	55 mm18 Feb 1984	80 mm1971 · driest 0 mm in 1949	132
March	37.2°C21 Mar 2026	-27.8°C4 Mar 1978	86 mm14 Mar 2021	223 mm1987 · driest 0 mm in 1988	134
April	36.7°C28 Apr 1910	-18.3°C3 Apr 1975	76 mm26 Apr 2024	192 mm1896 · driest 2 mm in 1928	134
May	40.6°C29 May 1934	-6.7°C2 May 1909	152 mm26 May 1964	291 mm1905 · driest 12 mm in 1934	132
June	42.2°C16 Jun 1946	1.7°C3 Jun 1969	132 mm5 Jun 1902	316 mm1967 · driest 13 mm in 1921	134
July	46.7°C24 Jul 1936	4.4°C21 Jul 1913	95 mm29 Jul 1966	251 mm1903 · driest 1 mm in 2012	132
August	43.3°C9 Aug 1936	2.8°C28 Aug 1988	104 mm13 Aug 1966	220 mm2017 · driest 1 mm in 1938	132
September	41.1°C1 Sep 1913	-6.1°C29 Sep 1984	152 mm11 Sep 1900	265 mm1900 · driest 2 mm in 2024	131
October	36.1°C11 Oct 2015	-16.7°C28 Oct 1925	97 mm16 Oct 1968	155 mm2008 · driest 0 mm in 1945	130
November	29.4°C3 Nov 2020	-25.6°C30 Nov 1964	65 mm16 Nov 1996	125 mm1983 · driest 0 mm in 1924	130
December	26.1°C6 Dec 1939	-33.3°C14 Dec 1901	51 mm1 Dec 2018	106 mm1913 · driest 0 mm in 1903	131

Typical days per month at GENOA 2 W, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	30	<1	5
February	<1	0	26	<1	4
March	1	<1	22	1	3
April	5	1	9	2	1
May	13	4	1	4	<1
June	25	12	0	3	0
July	29	17	0	2	0
August	27	13	0	3	0
September	19	8	<1	2	0
October	6	1	8	2	<1
November	<1	0	22	1	2
December	0	0	30	<1	4

How often, not how much — every day in GENOA 2 W’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	<1%	10%	1%	4%	-3.0–6.1°C
February	2%	12%	2%	6%	-1.4–9.0°C
March	14%	16%	4%	11%	4.9–14.7°C
April	35%	22%	8%	23%	14.9–20.7°C
May	56%	29%	11%	32%	20.9–26.1°C
June	71%	28%	12%	29%	25.9–31.1°C
July	78%	22%	9%	19%	28.5–34.2°C
August	77%	23%	9%	19%	27.6–33.2°C
September	73%	20%	8%	17%	23.4–29.1°C
October	47%	14%	5%	11%	16.1–22.7°C
November	9%	11%	3%	7%	7.1–13.8°C
December	<1%	11%	2%	6%	-1.1–6.9°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.

1893Each stripe is one year’s mean temperature against the 119-year average. Warmest: 1939. Coolest: 1978.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5068818
NOAA station: USC00253185 · GENOA 2 W
Station distance: 19.7 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 41.36°, 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 GENOA 2 W is what differs

Genoa→Saint Edward→Monroe→Krakow→Merchiston→Rosenburg→

Or put two places side by side: Fullerton vs Genoa

Best time to visitFullerton.