United States · 1991–2020

Best time to visit
Thornton.

September leads for comfortable weather in Thornton: typically 27.1°C by day, 9.2°C at night, with 27 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high27.1°C

Typical low9.2°C

Rain in September27 mm

Comfort

September

September · June · May

78climate match

Beach

June

June · August · July

71climate match

Outdoors

October

October · May · September

85climate match

The weakest month is December, scoring 8 against September’s 78 — days reach only 8.3°C, 16° below the 24°C the score treats as ideal, and nights drop to -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

98.5° / -7.1°

Feb

149.5° / -6.3°

Mar

3614.2° / -2.1°

Apr

5017.8° / 1.6°

May

7222.5° / 6.7°

Jun

7529.1° / 11.7°

Jul

6732.6° / 14.7°

Aug

7231.3° / 13.8°

Sep

7827.1° / 9.2°

Oct

6219.5° / 2.7°

Nov

3113° / -2.8°

Dec

88.3° / -7°

Monthly climate evidence for Thornton — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	8.5°C	-7.1°C	11 mm	2.7	9 h 38	9	Strong coverage
February	9.5°C	-6.3°C	14 mm	3.1	10 h 38	14	Strong coverage
March	14.2°C	-2.1°C	31 mm	4.1	11 h 49	36	Strong coverage
April	17.8°C	1.6°C	49 mm	6.4	13 h 12	50	Strong coverage
May	22.5°C	6.7°C	59 mm	7.8	14 h 21	72	Strong coverage
June	29.1°C	11.7°C	38 mm	5.5	14 h 59	75	Strong coverage
July	32.6°C	14.7°C	45 mm	5.6	14 h 44	67	Strong coverage
August	31.3°C	13.8°C	34 mm	5.3	13 h 44	72	Strong coverage
September	27.1°C	9.2°C	27 mm	4.2	12 h 24	78	Strong coverage
October	19.5°C	2.7°C	25 mm	3.8	11 h 05	62	Strong coverage
November	13°C	-2.8°C	18 mm	3.5	9 h 55	31	Strong coverage
December	8.3°C	-7°C	13 mm	2.9	9 h 21	8	Strong coverage

Records at NORTHGLENN, 1984–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	25.0°C2 Jan 1997	-26.1°C31 Jan 1985	17 mm12 Jan 2019	42 mm2019 · driest 0 mm in 2003	41
February	28.3°C11 Feb 2017	-27.2°C3 Feb 1996	25 mm4 Feb 2024	62 mm2024 · driest 0 mm in 2005	40
March	34.4°C26 Mar 2026	-20.6°C2 Mar 2002	51 mm27 Mar 2003	121 mm2003 · driest 0 mm in 2012	41
April	32.2°C13 Apr 2025	-14.4°C12 Apr 1997	58 mm24 Apr 1997	101 mm2009 · driest 1 mm in 2002	40
May	38.3°C29 May 2003	-6.7°C2 May 2013	56 mm29 May 1990	165 mm2015 · driest 6 mm in 2024	42
June	40.6°C29 Jun 2018	1.1°C1 Jun 1988	39 mm12 Jun 2010	116 mm2023 · driest 3 mm in 2012	41
July	42.2°C22 Jul 2005	6.1°C13 Jul 1987	55 mm24 Jul 2004	114 mm2014 · driest 0 mm in 2008	42
August	43.3°C2 Aug 2008	5.0°C28 Aug 2004	62 mm24 Aug 1992	91 mm2008 · driest 1 mm in 1985	41
September	38.9°C3 Sep 2019	-7.8°C29 Sep 1985	48 mm12 Sep 2013	162 mm2013 · driest 0 mm in 1992	42
October	33.9°C3 Oct 2024	-15.6°C31 Oct 2019	40 mm4 Oct 1984	86 mm1984 · driest 0 mm in 2003	39
November	28.9°C3 Nov 2025	-21.1°C24 Nov 1993	27 mm26 Nov 2019	66 mm2015 · driest 0 mm in 2011	42
December	27.8°C23 Dec 2025	-31.1°C22 Dec 1990	38 mm21 Dec 2006	70 mm2006 · driest 0 mm in 2002	42

Typical days per month at NORTHGLENN, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	28	<1	4
February	<1	0	26	<1	4
March	1	0	21	<1	4
April	5	<1	11	2	3
May	13	4	2	2	<1
June	24	15	0	1	0
July	29	24	0	1	0
August	29	22	0	<1	0
September	21	11	<1	<1	<1
October	8	1	8	<1	1
November	1	0	22	<1	3
December	0	0	29	<1	4

How often, not how much — every day in NORTHGLENN’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	3%	9%	<1%	3%	4.6–10.8°C
February	7%	12%	1%	7%	5.7–13.3°C
March	22%	14%	3%	8%	10.5–17.9°C
April	41%	20%	5%	18%	15.0–20.8°C
May	60%	24%	7%	25%	19.7–25.0°C
June	80%	18%	5%	17%	26.5–32.5°C
July	81%	18%	4%	20%	29.6–35.5°C
August	83%	16%	3%	11%	29.2–33.6°C
September	79%	14%	3%	9%	23.4–30.4°C
October	52%	11%	3%	6%	16.8–21.9°C
November	21%	11%	2%	4%	8.2–17.3°C
December	4%	9%	<1%	6%	4.7–11.2°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.

1985Each stripe is one year’s mean temperature against the 34-year average. Warmest: 2025. Coolest: 1985.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5441492
NOAA station: USC00055984 · NORTHGLENN
Station distance: 4.9 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 29 usable years
Daylight: Calculated from latitude 39.87°, 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 NORTHGLENN is what differs

Westminster→Broomfield→Northglenn→Lafayette→Sherrelwood→Welby→

Or put two places side by side: Thornton vs Westminster

Best time to visitThornton.