United States · 1991–2020

Best time to visit
Johnston.

September leads for comfortable weather in Johnston: typically 24.8°C by day, 12.8°C at night, with 86 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high24.8°C

Typical low12.8°C

Rain in September86 mm

Comfort

September

September · August · June

83climate match

Beach

July

July · August · June

76climate match

Outdoors

October

October · May · September

73climate match

The weakest month is January, scoring 5 against September’s 83 — days reach only -1.1°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

5-1.1° / -10.8°

Feb

51.5° / -8.6°

Mar

149° / -2°

Apr

4216.5° / 4.5°

May

6522° / 10.8°

Jun

6627.2° / 16.4°

Jul

6229.4° / 18.7°

Aug

6828.2° / 17.3°

Sep

8324.8° / 12.8°

Oct

5217.1° / 5.6°

Nov

189.2° / -1.2°

Dec

51.6° / -7.6°

Monthly climate evidence for Johnston — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	-1.1°C	-10.8°C	27 mm	4.9	9 h 28	5	Good coverage
February	1.5°C	-8.6°C	33 mm	5.5	10 h 32	5	Strong coverage
March	9°C	-2°C	53 mm	6.7	11 h 48	14	Strong coverage
April	16.5°C	4.5°C	101 mm	8.9	13 h 16	42	Strong coverage
May	22°C	10.8°C	131 mm	10.7	14 h 30	65	Strong coverage
June	27.2°C	16.4°C	141 mm	9.5	15 h 11	66	Strong coverage
July	29.4°C	18.7°C	102 mm	7	14 h 55	62	Strong coverage
August	28.2°C	17.3°C	106 mm	7.7	13 h 51	68	Strong coverage
September	24.8°C	12.8°C	86 mm	6.8	12 h 25	83	Strong coverage
October	17.1°C	5.6°C	67 mm	7	11 h 01	52	Strong coverage
November	9.2°C	-1.2°C	47 mm	5.3	9 h 46	18	Strong coverage
December	1.6°C	-7.6°C	37 mm	5.4	9 h 10	5	Strong coverage

Records at DES MOINES WSFO-JOHNSTON, 1995–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	19.4°C26 Jan 2002	-30.6°C2 Jan 2010	34 mm2 Jan 2023	70 mm2023 · driest 4 mm in 2025	30
February	25.0°C26 Feb 2024	-32.8°C2 Feb 1996	36 mm24 Feb 2007	62 mm2023 · driest 4 mm in 2022	31
March	33.3°C21 Mar 2026	-24.4°C3 Mar 2014	49 mm30 Mar 1998	118 mm2009 · driest 9 mm in 2000	31
April	31.7°C13 Apr 2006	-10.6°C4 Apr 2018	78 mm14 Apr 2012	182 mm2026 · driest 27 mm in 2021	31
May	35.6°C26 May 2018	-2.2°C3 May 2011	85 mm21 May 2024	276 mm2013 · driest 50 mm in 2006	31
June	37.8°C17 Jun 2021	5.0°C3 Jun 1998	109 mm25 Jun 2005	367 mm2010 · driest 16 mm in 2006	31
July	40.0°C23 Jul 2012	9.4°C10 Jul 1996	113 mm24 Jul 1997	311 mm2025 · driest 24 mm in 2001	31
August	39.4°C30 Aug 2013	7.8°C12 Aug 2004	101 mm10 Aug 2010	374 mm2010 · driest 8 mm in 2003	30
September	38.3°C9 Sep 2013	-1.1°C29 Sep 2003	93 mm25 Sep 2017	249 mm2018 · driest 16 mm in 1998	30
October	33.9°C3 Oct 1997	-8.9°C27 Oct 1997	71 mm24 Oct 2021	176 mm2009 · driest 4 mm in 1999	31
November	27.2°C13 Nov 1999	-19.4°C12 Nov 2019	90 mm3 Nov 2003	135 mm2003 · driest 4 mm in 2023	31
December	22.8°C15 Dec 2021	-28.3°C31 Dec 2017	60 mm13 Dec 2015	155 mm2015 · driest 0 mm in 2002	31

Typical days per month at DES MOINES WSFO-JOHNSTON, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	30	<1	7
February	0	0	26	1	6
March	<1	0	21	2	4
April	3	<1	7	3	1
May	11	2	<1	4	<1
June	22	9	0	4	0
July	28	14	0	3	0
August	26	10	0	3	0
September	16	5	<1	3	0
October	4	<1	5	2	<1
November	<1	0	18	2	2
December	0	0	28	1	6

How often, not how much — every day in DES MOINES WSFO-JOHNSTON’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%	15%	3%	10%	-3.5–0.9°C
February	<1%	18%	3%	14%	-3.4–7.1°C
March	10%	22%	6%	22%	5.9–13.3°C
April	26%	29%	11%	35%	14.1–19.4°C
May	48%	34%	13%	45%	20.2–24.4°C
June	68%	31%	14%	38%	25.7–29.3°C
July	77%	23%	11%	23%	27.2–31.3°C
August	75%	25%	10%	25%	26.5–30.1°C
September	70%	21%	9%	22%	22.5–27.3°C
October	33%	22%	7%	22%	14.0–19.9°C
November	8%	18%	5%	15%	4.9–12.6°C
December	<1%	17%	3%	12%	-2.0–5.1°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.

1996Each stripe is one year’s mean temperature against the 29-year average. Warmest: 2024. Coolest: 2014.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4862760
NOAA station: USC00132209 · DES MOINES WSFO-JOHNSTON
Station distance: 7.4 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 24 usable years
Daylight: Calculated from latitude 41.67°, 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 DES MOINES WSFO-JOHNSTON is what differs

Waukee→Grimes→Polk City→Dallas Center→Granger→Sheldahl→

Or put two places side by side: Johnston vs Waukee

Best time to visitJohnston.