United States · 1991–2020

Best time to visit
Keystone.

September leads for comfortable weather in Keystone: typically 24.3°C by day, 10.3°C at night, with 90 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high24.3°C

Typical low10.3°C

Rain in September90 mm

Comfort

September

September · August · June

80climate match

Beach

July

July · August · June

71climate match

Outdoors

September

September · May · October

73climate match

The weakest month is January, scoring 5 against September’s 80 — days reach only -2.1°C, 26° 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

5-2.1° / -12.1°

Feb

50.8° / -9.8°

Mar

97.9° / -3.6°

Apr

3715.6° / 2.6°

May

6521.7° / 9.2°

Jun

7026.9° / 15°

Jul

6728.8° / 16.9°

Aug

7427.8° / 15.2°

Sep

8024.3° / 10.3°

Oct

4817.2° / 3.6°

Nov

138.6° / -2.8°

Dec

51.1° / -8.6°

Monthly climate evidence for Keystone — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	-2.1°C	-12.1°C	27 mm	4.5	9 h 26	5	Strong coverage
February	0.8°C	-9.8°C	31 mm	4.8	10 h 31	5	Strong coverage
March	7.9°C	-3.6°C	50 mm	5.9	11 h 48	9	Strong coverage
April	15.6°C	2.6°C	95 mm	8.6	13 h 17	37	Strong coverage
May	21.7°C	9.2°C	112 mm	9.8	14 h 32	65	Strong coverage
June	26.9°C	15°C	136 mm	10.1	15 h 13	70	Strong coverage
July	28.8°C	16.9°C	105 mm	7.5	14 h 57	67	Strong coverage
August	27.8°C	15.2°C	100 mm	7.3	13 h 52	74	Strong coverage
September	24.3°C	10.3°C	90 mm	6.5	12 h 26	80	Strong coverage
October	17.2°C	3.6°C	73 mm	6.7	11 h	48	Strong coverage
November	8.6°C	-2.8°C	52 mm	5.1	9 h 45	13	Strong coverage
December	1.1°C	-8.6°C	39 mm	5.4	9 h 08	5	Strong coverage

What has changed

Keystone runs +0.7°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

+0.7

Feb

+0.6

Mar

+1.5

Apr

-0.6

May

-0.3

Jun

+0.6

Jul

-0.2

Aug

-0.2

Sep

+1.8

Oct

+0.6

Nov

+1.4

Dec

+2.9

September daytime highs, 2011–2025. Last recorded: 27.0°C.

Records at BELLE PLAINE, 1893–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	18.3°C31 Jan 1989	-38.9°C16 Jan 2009	83 mm12 Jan 1960	126 mm1960 · driest 0 mm in 1981	130
February	24.4°C27 Feb 2024	-37.2°C3 Feb 1996	64 mm9 Feb 1904	121 mm1905 · driest 1 mm in 1995	131
March	31.7°C22 Mar 2026	-30.6°C1 Mar 1962	55 mm19 Mar 1922	154 mm1991 · driest 0 mm in 1994	132
April	35.0°C25 Apr 1986	-13.9°C20 Apr 1904	70 mm24 Apr 1965	215 mm1954 · driest 15 mm in 1942	132
May	42.2°C31 May 1934	-5.6°C3 May 2005	92 mm6 May 1960	292 mm1974 · driest 11 mm in 1992	132
June	41.1°C28 Jun 1934	1.7°C4 Jun 1945	134 mm23 Jun 2007	319 mm1947 · driest 25 mm in 1988	132
July	42.8°C26 Jul 1936	5.6°C26 Jul 1911	162 mm14 Jul 1962	342 mm1907 · driest 2 mm in 1894	132
August	43.9°C18 Aug 1936	2.2°C20 Aug 1950	164 mm2 Aug 1929	348 mm1993 · driest 7 mm in 2003	129
September	40.0°C4 Sep 1925	-5.0°C30 Sep 1899	134 mm16 Sep 1921	292 mm1926 · driest 6 mm in 2024	131
October	33.9°C6 Oct 1963	-18.9°C30 Oct 1925	95 mm2 Oct 2019	189 mm1941 · driest 1 mm in 1952	129
November	27.8°C1 Nov 1924	-23.3°C26 Nov 1977	90 mm4 Nov 2003	231 mm1934 · driest 1 mm in 1989	130
December	21.1°C4 Dec 2012	-34.4°C19 Dec 1985	51 mm20 Dec 1895	140 mm2015 · driest 1 mm in 2002	131

Typical days per month at BELLE PLAINE, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	30	<1	5
February	0	0	27	<1	4
March	<1	0	23	2	2
April	3	<1	10	3	<1
May	10	2	<1	4	0
June	22	8	0	4	0
July	27	12	0	4	0
August	25	9	0	3	0
September	15	4	<1	3	0
October	4	<1	10	2	<1
November	<1	0	22	2	1
December	0	0	28	1	4

The best month has moved. On the 1961–1990 numbers the strongest month here was September (scoring 84); on 2011–2025 it is August (81). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in BELLE PLAINE’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%	16%	3%	11%	-6.2–2.3°C
February	<1%	18%	3%	13%	-3.1–4.9°C
March	6%	22%	7%	22%	3.7–12.1°C
April	23%	29%	10%	34%	12.7–19.1°C
May	48%	32%	11%	39%	19.8–25.4°C
June	67%	31%	13%	36%	25.0–29.6°C
July	75%	25%	11%	24%	27.4–31.8°C
August	76%	24%	10%	22%	26.4–30.8°C
September	63%	24%	10%	25%	22.0–27.1°C
October	34%	21%	7%	21%	14.8–20.9°C
November	5%	18%	6%	14%	5.0–11.5°C
December	<1%	17%	4%	13%	-3.2–4.6°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.

1893Each stripe is one year’s mean temperature against the 121-year average. Warmest: 1931. Coolest: 1996.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4863425
NOAA station: USC00130600 · BELLE PLAINE
Station distance: 14.6 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 27 usable years
Daylight: Calculated from latitude 42.00°, 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 BELLE PLAINE is what differs

Belle Plaine→Brooklyn→Victor→Blairstown→Holiday Lake→Ladora→

Or put two places side by side: Keystone vs Belle Plaine

Best time to visitKeystone.

September

July

September

The whole year,without the guesswork.

Keystone runs +0.7°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Keystone.

The whole year,
without the guesswork.

Keystone runs +0.7°C
on the 1961–1990 baseline.

Nearby, measured,
and named.