United States · 1991–2020

Best time to visit
Ashburn.

September leads for comfortable weather in Ashburn: typically 26.4°C by day, 13.1°C at night, with 105 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high26.4°C

Typical low13.1°C

Rain in September105 mm

Comfort

September

September · May · June

75climate match

Beach

August

August · July · June

71climate match

Outdoors

October

October · April · May

77climate match

The weakest month is January, scoring 5 against September’s 75 — days reach only 5.8°C, 18° below the 24°C the score treats as ideal, and nights drop to -5.3°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

55.8° / -5.3°

Feb

57.6° / -4.5°

Mar

2012.3° / -0.7°

Apr

5319.1° / 4.8°

May

7223.7° / 10.5°

Jun

6828.4° / 15.5°

Jul

5630.9° / 18.1°

Aug

6430.1° / 17.1°

Sep

7526.4° / 13.1°

Oct

5820.1° / 6.1°

Nov

2913.6° / 0.5°

Dec

58.1° / -3.2°

Monthly climate evidence for Ashburn — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	5.8°C	-5.3°C	79 mm	8.1	9 h 42	5	Strong coverage
February	7.6°C	-4.5°C	66 mm	7.3	10 h 40	5	Strong coverage
March	12.3°C	-0.7°C	96 mm	8.7	11 h 50	20	Strong coverage
April	19.1°C	4.8°C	88 mm	8.9	13 h 10	53	Strong coverage
May	23.7°C	10.5°C	123 mm	9.8	14 h 17	72	Strong coverage
June	28.4°C	15.5°C	115 mm	9	14 h 54	68	Strong coverage
July	30.9°C	18.1°C	103 mm	9.3	14 h 39	56	Strong coverage
August	30.1°C	17.1°C	94 mm	7.4	13 h 41	64	Strong coverage
September	26.4°C	13.1°C	105 mm	7.6	12 h 24	75	Strong coverage
October	20.1°C	6.1°C	103 mm	6.9	11 h 06	58	Strong coverage
November	13.6°C	0.5°C	82 mm	6.8	9 h 59	29	Strong coverage
December	8.1°C	-3.2°C	90 mm	8.3	9 h 26	5	Strong coverage

Records at WFO STERLING, 1977–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C26 Jan 2024	-28.3°C27 Jan 1987	72 mm31 Jan 2013	192 mm1978 · driest 11 mm in 1981	48
February	26.7°C26 Feb 2000	-27.2°C18 Feb 1979	69 mm6 Feb 2010	173 mm2003 · driest 7 mm in 1978	49
March	32.2°C13 Mar 1990	-18.9°C15 Mar 1993	74 mm7 Mar 2011	179 mm1994 · driest 1 mm in 2006	49
April	35.0°C18 Apr 2002	-8.3°C10 Apr 1985	70 mm21 Apr 2008	193 mm1983 · driest 16 mm in 1985	49
May	35.6°C18 May 2026	-2.2°C10 May 1983	104 mm12 May 2008	244 mm2008 · driest 6 mm in 2007	48
June	38.3°C30 Jun 2012	2.2°C3 Jun 1986	119 mm26 Jun 2006	277 mm2006 · driest 19 mm in 1988	49
July	40.0°C23 Jul 2011	3.9°C1 Jul 1988	112 mm21 Jul 2018	251 mm2017 · driest 21 mm in 1983	49
August	40.0°C21 Aug 1983	2.2°C29 Aug 1982	147 mm11 Aug 1984	289 mm1984 · driest 8 mm in 1998	48
September	37.2°C11 Sep 2016	-1.1°C28 Sep 1989	169 mm7 Sep 2008	282 mm2011 · driest 6 mm in 2005	49
October	35.0°C2 Oct 2019	-7.2°C31 Oct 1988	147 mm30 Oct 2012	271 mm2005 · driest 2 mm in 2000	49
November	28.3°C2 Nov 1982	-13.3°C24 Nov 1989	117 mm28 Nov 1993	192 mm2018 · driest 7 mm in 1981	49
December	27.2°C8 Dec 1998	-20.6°C25 Dec 1989	63 mm15 Dec 2018	171 mm2009 · driest 12 mm in 2021	49

Typical days per month at WFO STERLING, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	26	3	3
February	<1	0	23	2	3
March	1	<1	18	3	2
April	6	2	6	3	<1
May	14	5	<1	4	0
June	25	12	0	4	0
July	30	20	0	3	0
August	29	18	0	3	0
September	19	7	0	3	0
October	6	<1	5	3	0
November	<1	0	16	3	<1
December	<1	0	23	3	2

How often, not how much — every day in WFO STERLING’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%	26%	8%	28%	2.4–8.5°C
February	3%	26%	8%	30%	3.5–10.8°C
March	12%	27%	10%	31%	9.1–15.6°C
April	34%	29%	9%	33%	16.9–21.2°C
May	56%	33%	14%	40%	21.7–25.6°C
June	71%	29%	11%	34%	26.7–29.7°C
July	71%	29%	10%	33%	29.0–32.7°C
August	74%	25%	10%	27%	28.1–31.7°C
September	73%	24%	10%	25%	24.7–28.7°C
October	43%	22%	10%	21%	18.1–22.0°C
November	13%	23%	9%	24%	11.1–16.2°C
December	2%	25%	9%	25%	5.2–11.4°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.

1978Each stripe is one year’s mean temperature against the 46-year average. Warmest: 2024. Coolest: 1978.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4744870
NOAA station: USC00448084 · WFO STERLING
Station distance: 7.5 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 39.04°, 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 WFO STERLING is what differs

Sterling→Broadlands→Sugarland Run→Lowes Island→Countryside→Brambleton→

Or put two places side by side: Ashburn vs Sterling

Best time to visitAshburn.