United States · 1991–2020

Best time to visit
Herndon.

September leads for comfortable weather in Herndon: typically 27.1°C by day, 10.3°C at night, with 44 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high27.1°C

Typical low10.3°C

Rain in September44 mm

Comfort

September

September · May · June

79climate match

Beach

August

August · June · July

67climate match

Outdoors

October

October · April · September

84climate match

The weakest month is January, scoring 5 against September’s 79 — days reach only 5.4°C, 19° below the 24°C the score treats as ideal, and nights drop to -9.7°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

55.4° / -9.7°

Feb

57.2° / -8.4°

Mar

2913.2° / -4°

Apr

5218.3° / 1.6°

May

7423.3° / 7.6°

Jun

6929.8° / 14°

Jul

5632.8° / 17.2°

Aug

6431.3° / 15.9°

Sep

7927.1° / 10.3°

Oct

6219.8° / 2.5°

Nov

2612.2° / -4.2°

Dec

55.9° / -9°

Monthly climate evidence for Herndon — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	5.4°C	-9.7°C	11 mm	2	9 h 38	5	Strong coverage
February	7.2°C	-8.4°C	17 mm	2.9	10 h 37	5	Strong coverage
March	13.2°C	-4°C	27 mm	3.9	11 h 49	29	Strong coverage
April	18.3°C	1.6°C	54 mm	5.6	13 h 12	52	Strong coverage
May	23.3°C	7.6°C	81 mm	7.8	14 h 21	74	Strong coverage
June	29.8°C	14°C	81 mm	7.6	14 h 59	69	Strong coverage
July	32.8°C	17.2°C	87 mm	7.1	14 h 44	56	Strong coverage
August	31.3°C	15.9°C	80 mm	7	13 h 44	64	Strong coverage
September	27.1°C	10.3°C	44 mm	4.6	12 h 24	79	Strong coverage
October	19.8°C	2.5°C	40 mm	4.3	11 h 04	62	Strong coverage
November	12.2°C	-4.2°C	20 mm	2.8	9 h 55	26	Strong coverage
December	5.9°C	-9°C	17 mm	2.7	9 h 21	5	Strong coverage

What has changed

Herndon runs -0.6°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

-2.3

Mar

+1.2

Apr

-1.2

May

-1.7

Jun

+0.1

Jul

-0.9

Aug

-1.4

Sep

0.0

Oct

-1.8

Nov

+1.1

Dec

-0.5

September daytime highs, 2011–2020. Last recorded: 26.8°C.

Records at OBERLIN, 1913–2021
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.6°C28 Jan 2015	-35.6°C11 Jan 1918	36 mm20 Jan 1990	49 mm1944 · driest 0 mm in 1961	107
February	29.4°C17 Feb 1970	-33.3°C8 Feb 1933	48 mm11 Feb 1993	81 mm1993 · driest 0 mm in 1916	108
March	33.9°C30 Mar 1943	-31.7°C11 Mar 1948	44 mm18 Mar 1984	142 mm1987 · driest 0 mm in 2009	107
April	36.1°C23 Apr 1989	-17.8°C2 Apr 1936	66 mm17 Apr 2016	162 mm2016 · driest 3 mm in 1928	107
May	39.4°C30 May 2000	-5.6°C1 May 1966	90 mm24 May 2008	215 mm1923 · driest 3 mm in 1966	107
June	43.9°C27 Jun 2012	1.1°C2 Jun 1917	120 mm13 Jun 1965	245 mm1965 · driest 4 mm in 1918	107
July	45.6°C24 Jul 1936	4.4°C31 Jul 1925	131 mm16 Jul 1979	245 mm1944 · driest 6 mm in 1934	108
August	43.3°C11 Aug 1936	1.7°C24 Aug 1928	78 mm4 Aug 1920	182 mm1993 · driest 5 mm in 1919	109
September	41.7°C2 Sep 1939	-7.2°C25 Sep 1926	70 mm15 Sep 1970	200 mm1965 · driest 0 mm in 1974	107
October	37.2°C5 Oct 1947	-16.7°C27 Oct 2020	78 mm29 Oct 2000	160 mm1946 · driest 0 mm in 1939	107
November	31.1°C6 Nov 1980	-28.3°C14 Nov 1940	82 mm4 Nov 1922	87 mm1975 · driest 0 mm in 1914	108
December	28.3°C23 Dec 1964	-35.0°C22 Dec 1989	39 mm5 Dec 1913	139 mm1913 · driest 0 mm in 2000	107

Typical days per month at OBERLIN, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	30	<1	2
February	<1	0	27	<1	3
March	2	<1	25	<1	2
April	6	2	12	2	<1
May	13	5	2	3	<1
June	25	15	0	3	0
July	29	23	0	3	0
August	28	20	0	2	0
September	20	11	<1	1	0
October	8	2	10	1	<1
November	2	0	25	<1	1
December	0	0	30	<1	2

The best month has moved. On the 1961–1990 numbers the strongest month here was May (scoring 78); on 2011–2025 it is September (78). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in OBERLIN’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	2%	7%	<1%	2%	0.9–9.6°C
February	8%	11%	1%	7%	2.4–12.4°C
March	23%	14%	3%	10%	8.8–17.2°C
April	45%	19%	6%	17%	16.1–21.9°C
May	63%	24%	9%	26%	21.4–26.9°C
June	74%	25%	9%	26%	27.6–33.2°C
July	79%	21%	8%	18%	31.0–36.5°C
August	80%	21%	7%	17%	29.7–35.0°C
September	79%	15%	5%	11%	25.3–30.8°C
October	59%	12%	4%	8%	17.5–24.4°C
November	17%	9%	2%	4%	9.7–15.7°C
December	3%	8%	1%	4%	2.6–9.6°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 99-year average. Warmest: 1954. Coolest: 1993.2019

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5445588
NOAA station: USC00145906 · OBERLIN
Station distance: 24.9 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 28 usable years
Daylight: Calculated from latitude 39.91°, 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 OBERLIN is what differs

Oberlin→Jennings→Dresden→Kanona→Midway→Traer→

Or put two places side by side: Herndon vs Oberlin

Best time to visitHerndon.