United States · 1991–2020

Best time to visit
Deerfield.

September leads for comfortable weather in Deerfield: typically 23.5°C by day, 11.2°C at night, with 88 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high23.5°C

Typical low11.2°C

Rain in September88 mm

Comfort

September

September · August · June

80climate match

Beach

July

July · August · June

70climate match

Outdoors

May

May · September · October

74climate match

The weakest month is January, scoring 5 against September’s 80 — days reach only -2.6°C, 27° 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

5-2.6° / -11.1°

Feb

5-0.2° / -9.5°

Mar

56.3° / -3.9°

Apr

3214.2° / 2.3°

May

6321.1° / 8.7°

Jun

6926.6° / 14.5°

Jul

6728.7° / 16.9°

Aug

7327.2° / 15.8°

Sep

8023.5° / 11.2°

Oct

4616° / 4.7°

Nov

127.8° / -1.4°

Dec

50.5° / -7.5°

Monthly climate evidence for Deerfield — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	-2.6°C	-11.1°C	46 mm	6	9 h 20	5	Strong coverage
February	-0.2°C	-9.5°C	34 mm	5.2	10 h 27	5	Strong coverage
March	6.3°C	-3.9°C	51 mm	5.9	11 h 47	5	Strong coverage
April	14.2°C	2.3°C	93 mm	8.4	13 h 20	32	Strong coverage
May	21.1°C	8.7°C	109 mm	9.7	14 h 38	63	Strong coverage
June	26.6°C	14.5°C	144 mm	9.7	15 h 21	69	Strong coverage
July	28.7°C	16.9°C	108 mm	7.6	15 h 04	67	Strong coverage
August	27.2°C	15.8°C	114 mm	7.8	13 h 56	73	Strong coverage
September	23.5°C	11.2°C	88 mm	7.2	12 h 26	80	Strong coverage
October	16°C	4.7°C	71 mm	7.5	10 h 57	46	Strong coverage
November	7.8°C	-1.4°C	53 mm	6.1	9 h 39	12	Strong coverage
December	0.5°C	-7.5°C	46 mm	6.3	9 h 01	5	Strong coverage

What has changed

Deerfield runs +0.0°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

+0.3

Feb

-0.6

Mar

+0.5

Apr

-1.6

May

-0.6

Jun

+0.1

Jul

-0.2

Aug

-0.1

Sep

+1.0

Oct

-0.1

Nov

-0.1

Dec

+1.7

September daytime highs, 2011–2025. Last recorded: 25.3°C.

Records at LAKE MILLS WWTP, 1893–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	15.6°C26 Jan 1944	-36.1°C30 Jan 1951	50 mm27 Jan 1916	101 mm1916 · driest 1 mm in 2002	132
February	21.7°C28 Feb 2024	-35.6°C20 Feb 1929	42 mm22 Feb 1981	93 mm2023 · driest 0 mm in 1987	132
March	28.9°C22 Mar 2012	-27.8°C1 Mar 1962	63 mm15 Mar 1959	158 mm2009 · driest 0 mm in 2001	130
April	31.7°C10 Apr 1930	-13.3°C7 Apr 1982	79 mm23 Apr 1999	226 mm1999 · driest 10 mm in 1932	131
May	39.4°C31 May 1934	-6.7°C2 May 1945	81 mm17 May 1999	260 mm1912 · driest 14 mm in 1925	132
June	40.0°C1 Jun 1934	-1.7°C3 Jun 1929	86 mm16 Jun 1894	289 mm2008 · driest 9 mm in 2012	131
July	43.3°C14 Jul 1936	4.4°C31 Jul 1918	112 mm17 Jul 1903	305 mm1902 · driest 2 mm in 1909	132
August	40.0°C1 Aug 1988	1.1°C30 Aug 1915	142 mm19 Aug 2007	451 mm2007 · driest 11 mm in 1901	131
September	37.8°C7 Sep 1939	-4.4°C30 Sep 1899	130 mm8 Sep 1941	262 mm1965 · driest 4 mm in 1932	130
October	32.2°C1 Oct 1897	-19.4°C30 Oct 1925	80 mm17 Oct 1905	185 mm1919 · driest 3 mm in 1952	129
November	25.0°C7 Nov 1915	-25.0°C29 Nov 1976	76 mm5 Nov 2003	190 mm1934 · driest 1 mm in 1998	130
December	18.9°C4 Dec 1998	-31.1°C24 Dec 1983	42 mm14 Dec 2015	123 mm2007 · driest 0 mm in 2003	130

Typical days per month at LAKE MILLS WWTP, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	27	1	7
February	0	0	25	1	6
March	<1	0	22	2	3
April	2	<1	9	4	<1
May	8	3	<1	4	0
June	20	7	0	4	0
July	27	11	0	4	0
August	23	7	0	3	0
September	13	3	<1	3	0
October	2	<1	5	2	<1
November	0	0	18	2	2
December	0	0	26	1	6

The best month has moved. On the 1961–1990 numbers the strongest month here was June (scoring 80); on 2011–2025 it is September (85). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in LAKE MILLS WWTP’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%	20%	3%	15%	-6.1–0.8°C
February	<1%	18%	3%	13%	-4.4–3.1°C
March	3%	23%	6%	21%	2.2–9.5°C
April	16%	29%	10%	34%	11.4–17.2°C
May	43%	31%	12%	36%	18.3–24.0°C
June	65%	30%	12%	33%	23.6–28.4°C
July	76%	24%	10%	22%	26.8–31.0°C
August	75%	24%	11%	22%	25.3–29.4°C
September	58%	25%	11%	27%	21.0–25.9°C
October	26%	23%	7%	23%	13.9–19.3°C
November	2%	22%	6%	18%	4.6–10.6°C
December	0%	20%	4%	16%	-3.6–3.4°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.

1893Each stripe is one year’s mean temperature against the 122-year average. Warmest: 2012. Coolest: 1917.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5250368
NOAA station: USC00474482 · LAKE MILLS WWTP
Station distance: 14.9 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 28 usable years
Daylight: Calculated from latitude 43.05°, 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 LAKE MILLS WWTP is what differs

Lake Mills→Lake Ripley→Cambridge→Aztalan→Milford→Hoopers Mill→

Or put two places side by side: Deerfield vs Lake Mills

Best time to visitDeerfield.

September

July

May

The whole year,without the guesswork.

Deerfield runs +0.0°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Deerfield.

The whole year,
without the guesswork.

Deerfield runs +0.0°C
on the 1961–1990 baseline.

Nearby, measured,
and named.