United States · 1991–2020

Best time to visit
St. Charles.

September leads for comfortable weather in St. Charles: typically 24.5°C by day, 11.8°C at night, with 79 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high24.5°C

Typical low11.8°C

Rain in September79 mm

Comfort

September

September · June · August

83climate match

Beach

July

July · August · June

74climate match

Outdoors

May

May · September · October

70climate match

The weakest month is January, scoring 5 against September’s 83 — days reach only -0.6°C, 25° below the 24°C the score treats as ideal.

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

5-0.6° / -9.1°

Feb

51.7° / -7.7°

Mar

128.5° / -2.4°

Apr

3815.6° / 3.1°

May

6421.7° / 9.2°

Jun

7626.8° / 14.6°

Jul

6828.9° / 17°

Aug

7427.8° / 16.1°

Sep

8324.5° / 11.8°

Oct

4916.9° / 5.3°

Nov

189.2° / -0.6°

Dec

52° / -6.4°

Monthly climate evidence for St. Charles — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	-0.6°C	-9.1°C	31 mm	5.3	9 h 26	5	Good coverage
February	1.7°C	-7.7°C	32 mm	4.7	10 h 31	5	Good coverage
March	8.5°C	-2.4°C	49 mm	6.8	11 h 48	12	Good coverage
April	15.6°C	3.1°C	90 mm	9.3	13 h 17	38	Good coverage
May	21.7°C	9.2°C	116 mm	10.6	14 h 32	64	Good coverage
June	26.8°C	14.6°C	94 mm	9.1	15 h 13	76	Good coverage
July	28.9°C	17°C	90 mm	8.1	14 h 56	68	Good coverage
August	27.8°C	16.1°C	88 mm	7.2	13 h 52	74	Good coverage
September	24.5°C	11.8°C	79 mm	7.2	12 h 26	83	Good coverage
October	16.9°C	5.3°C	80 mm	7.9	11 h 00	49	Good coverage
November	9.2°C	-0.6°C	50 mm	6.1	9 h 45	18	Good coverage
December	2°C	-6.4°C	42 mm	5.7	9 h 08	5	Good coverage

Records at CHICAGO W CHICAGO DUPAGE AP, 1997–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	18.3°C7 Jan 2008	-33.8°C31 Jan 2019	34 mm29 Jan 2013	76 mm2013 · driest 5 mm in 2004	29
February	23.3°C27 Feb 2024	-28.8°C10 Feb 2011	45 mm26 Feb 2009	81 mm2023 · driest 2 mm in 2003	29
March	28.3°C20 Mar 2012	-22.8°C4 Mar 2002	47 mm30 Mar 2017	116 mm2026 · driest 13 mm in 2015	29
April	31.1°C18 Apr 2002	-8.8°C7 Apr 2018	59 mm18 Apr 2013	165 mm1999 · driest 24 mm in 2021	29
May	35.6°C27 May 2012	-3.3°C21 May 2002	94 mm14 May 2020	196 mm2019 · driest 31 mm in 2023	29
June	37.2°C28 Jun 2012	1.1°C1 Jun 2003	79 mm15 Jun 2015	204 mm2015 · driest 13 mm in 2020	30
July	37.8°C7 Jul 2012	5.6°C2 Jul 2001	81 mm28 Jul 2023	244 mm2023 · driest 30 mm in 2018	30
August	36.1°C2 Aug 2006	6.1°C31 Aug 2009	73 mm13 Aug 2002	158 mm2002 · driest 24 mm in 2020	29
September	35.0°C2 Sep 2008	0.0°C24 Sep 2012	153 mm13 Sep 2008	312 mm2008 · driest 8 mm in 2017	29
October	31.7°C4 Oct 2025	-6.1°C28 Oct 1997	99 mm14 Oct 2017	211 mm2017 · driest 16 mm in 2005	29
November	24.4°C1 Nov 2016	-15.5°C22 Nov 2015	36 mm6 Nov 2000	120 mm2003 · driest 13 mm in 2002	29
December	20.6°C3 Dec 2012	-26.0°C19 Dec 2016	39 mm27 Dec 2008	130 mm2015 · driest 15 mm in 2014	29

Typical days per month at CHICAGO W CHICAGO DUPAGE AP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)
January	0	0	29	1
February	0	0	25	1
March	<1	0	21	2
April	3	<1	8	3
May	10	2	<1	4
June	21	8	0	3
July	27	13	0	3
August	25	8	0	3
September	15	4	0	2
October	4	<1	5	3
November	0	0	17	2
December	0	0	27	1

How often, not how much — every day in CHICAGO W CHICAGO DUPAGE 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	0%	17%	3%	13%	-3.1–2.7°C
February	<1%	16%	3%	11%	-4.1–6.3°C
March	5%	23%	5%	27%	6.4–12.7°C
April	19%	31%	9%	40%	13.9–17.9°C
May	45%	32%	12%	41%	19.9–24.1°C
June	67%	30%	11%	39%	25.2–29.0°C
July	73%	27%	11%	31%	26.8–30.6°C
August	76%	23%	9%	25%	26.3–29.2°C
September	67%	23%	7%	26%	22.8–26.7°C
October	25%	25%	8%	26%	15.3–19.5°C
November	5%	20%	5%	19%	5.5–12.6°C
December	<1%	18%	5%	13%	-1.3–5.4°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.

1998Each stripe is one year’s mean temperature against the 28-year average. Warmest: 2024. Coolest: 2014.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4908737
NOAA station: USW00094892 · CHICAGO W CHICAGO DUPAGE AP
Station distance: 5.2 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 22 usable years
Daylight: Calculated from latitude 41.91°, 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 CHICAGO W CHICAGO DUPAGE AP is what differs

Carol Stream→West Chicago→Batavia→Wasco→Geneva→Village of Campton Hills→

Or put two places side by side: St. Charles vs Carol Stream

Best time to visitSt. Charles.

September

July

May

The whole year,without the guesswork.

Nearby, measured,and named.

Best time to visit
St. Charles.

The whole year,
without the guesswork.

Nearby, measured,
and named.