United States · 1991–2020

Best time to visit
River Forest.

September leads for comfortable weather in River Forest: typically 24°C by day, 13.2°C at night, with 81 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high24°C

Typical low13.2°C

Rain in September81 mm

Comfort

September

September · June · August

87climate match

Beach

July

July · August · June

77climate match

Outdoors

May

May · September · October

73climate match

The weakest month is January, scoring 5 against September’s 87 — days reach only -0.4°C, 24° 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

5-0.4° / -8.2°

Feb

51.9° / -6.5°

Mar

108.2° / -1.4°

Apr

3614.9° / 3.8°

May

6421.2° / 9.6°

Jun

7626.7° / 15.2°

Jul

6529° / 18.3°

Aug

6827.9° / 17.6°

Sep

8724° / 13.2°

Oct

5016.9° / 6.6°

Nov

169° / 0.4°

Dec

52.4° / -5°

Monthly climate evidence for River Forest — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 16 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	-0.4°C	-8.2°C	50 mm	7.5	3.3°C	9 h 26	5	Strong coverage
February	1.9°C	-6.5°C	50 mm	6.4	2.0°C	10 h 31	5	Strong coverage
March	8.2°C	-1.4°C	62 mm	8.1	2.0°C	11 h 48	10	Strong coverage
April	14.9°C	3.8°C	95 mm	9.4	3.8°C	13 h 17	36	Strong coverage
May	21.2°C	9.6°C	114 mm	10.2	7.1°C	14 h 32	64	Strong coverage
June	26.7°C	15.2°C	105 mm	8.3	14.1°C	15 h 12	76	Strong coverage
July	29°C	18.3°C	94 mm	7.4	20.9°C	14 h 56	65	Strong coverage
August	27.9°C	17.6°C	108 mm	8.2	22.5°C	13 h 52	68	Strong coverage
September	24°C	13.2°C	81 mm	7	20.1°C	12 h 26	87	Strong coverage
October	16.9°C	6.6°C	87 mm	8.1	14.5°C	11 h 00	50	Strong coverage
November	9°C	0.4°C	61 mm	7.3	9.2°C	9 h 45	16	Strong coverage
December	2.4°C	-5°C	53 mm	7.3	5.6°C	9 h 09	5	Strong coverage

What has changed

River Forest runs +1.0°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

+1.6

Feb

+1.3

Mar

+1.6

Apr

0.0

May

+0.6

Jun

+1.1

Jul

+0.6

Aug

+0.7

Sep

+1.1

Oct

+0.2

Nov

+0.2

Dec

+2.5

September daytime highs, 2011–2025. Last recorded: 26.0°C.

Records at CHICAGO OHARE INTL AP, 1958–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	18.3°C7 Jan 2008	-32.8°C20 Jan 1985	51 mm12 Jan 1960	114 mm1999 · driest 3 mm in 1981	68
February	23.3°C27 Feb 2024	-28.3°C3 Feb 1996	87 mm21 Feb 1997	141 mm1997 · driest 3 mm in 1969	68
March	31.1°C29 Mar 1986	-22.2°C1 Mar 1962	47 mm30 Mar 2017	150 mm1976 · driest 16 mm in 1981	68
April	32.8°C22 Apr 1980	-13.9°C7 Apr 1982	90 mm18 Apr 2013	221 mm2013 · driest 18 mm in 2021	68
May	36.1°C27 May 2018	-4.4°C10 May 1966	90 mm14 May 2020	242 mm2020 · driest 8 mm in 1992	68
June	40.0°C20 Jun 1988	2.2°C11 Jun 1972	101 mm19 Jun 2009	253 mm1993 · driest 19 mm in 2005	68
July	40.0°C13 Jul 1995	4.4°C1 Jul 1965	174 mm23 Jul 2011	283 mm2011 · driest 29 mm in 2018	68
August	38.3°C2 Aug 1991	5.0°C29 Aug 1965	165 mm14 Aug 1987	434 mm1987 · driest 13 mm in 1969	67
September	37.2°C7 Sep 1960	-2.2°C23 Sep 1974	169 mm13 Sep 2008	346 mm2008 · driest 1 mm in 1979	67
October	32.8°C6 Oct 1963	-8.3°C24 Oct 1981	108 mm10 Oct 1969	221 mm2017 · driest 4 mm in 1964	67
November	25.6°C5 Nov 1978	-17.2°C30 Nov 1958	74 mm27 Nov 1990	209 mm1985 · driest 11 mm in 1999	68
December	21.7°C2 Dec 1982	-31.7°C24 Dec 1983	114 mm2 Dec 1982	218 mm1982 · driest 6 mm in 1962	68

Typical days per month at CHICAGO OHARE INTL AP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	28	2	8
February	0	0	25	1	6
March	<1	0	20	2	4
April	2	<1	6	3	1
May	9	3	<1	4	0
June	21	9	0	3	0
July	27	14	0	3	0
August	25	10	0	3	0
September	14	4	<1	2	0
October	3	<1	3	3	<1
November	0	0	15	2	2
December	0	0	25	2	6

How often, not how much — every day in CHICAGO OHARE INTL 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%	24%	4%	25%	-4.7–2.3°C
February	<1%	22%	4%	22%	-2.5–5.6°C
March	6%	28%	7%	34%	4.8–11.7°C
April	17%	32%	11%	39%	12.6–17.4°C
May	42%	30%	10%	36%	18.6–24.1°C
June	67%	27%	11%	31%	24.8–28.8°C
July	74%	25%	10%	28%	26.9–31.0°C
August	74%	25%	10%	25%	26.2–29.6°C
September	61%	24%	9%	26%	22.1–26.1°C
October	26%	24%	7%	25%	14.6–19.3°C
November	4%	25%	7%	28%	5.6–11.8°C
December	<1%	24%	5%	24%	-1.7–5.6°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.

1959Each stripe is one year’s mean temperature against the 67-year average. Warmest: 2024. Coolest: 1985.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4907637
NOAA station: USW00094846 · CHICAGO OHARE INTL AP
Station distance: 12 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 41.90°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 16 km from the place centre. A sheltered bay can run warmer than the open sea it is measured from.
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 OHARE INTL AP is what differs

Belmont Cragin→Portage Park→Des Plaines→Irving Park→Albany Park→Elmhurst→

Or put two places side by side: River Forest vs Belmont Cragin

Best time to visitRiver Forest.

September

July

May

The whole year,without the guesswork.

River Forest runs +1.0°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
River Forest.

The whole year,
without the guesswork.

River Forest runs +1.0°C
on the 1961–1990 baseline.

Nearby, measured,
and named.