United States · 1991–2020

Best time to visit
Boise.

September leads for comfortable weather in Boise: typically 26.7°C by day, 11.2°C at night, with 11 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high26.7°C

Typical low11.2°C

Rain in September11 mm

Comfort

September

September · June · May

84climate match

Beach

August

August · July · June

75climate match

Outdoors

May

May · October · September

85climate match

The weakest month is January, scoring 5 against September’s 84 — days reach only 3.8°C, 20° 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

53.8° / -3.8°

Feb

147.8° / -1.8°

Mar

3513° / 1.4°

Apr

5316.8° / 3.9°

May

7922.4° / 8.3°

Jun

8327.4° / 12.1°

Jul

6533.7° / 16.4°

Aug

7032.6° / 15.9°

Sep

8426.7° / 11.2°

Oct

6218.2° / 5°

Nov

219.3° / -0.3°

Dec

53.8° / -3.8°

Monthly climate evidence for Boise — daylight is calculated from latitude, everything else is measured
Month	Day	Night	Rain	Wet days	Daylight	Comfort	Coverage
January	3.8°C	-3.8°C	36 mm	7.6	9 h 16	5	Strong coverage
February	7.8°C	-1.8°C	25 mm	5.9	10 h 25	14	Strong coverage
March	13°C	1.4°C	34 mm	7.3	11 h 47	35	Strong coverage
April	16.8°C	3.9°C	31 mm	6.6	13 h 21	53	Strong coverage
May	22.4°C	8.3°C	37 mm	6.4	14 h 41	79	Strong coverage
June	27.4°C	12.1°C	19 mm	3.5	15 h 25	83	Strong coverage
July	33.7°C	16.4°C	5 mm	1.3	15 h 08	65	Strong coverage
August	32.6°C	15.9°C	4 mm	1	13 h 59	70	Strong coverage
September	26.7°C	11.2°C	11 mm	2.2	12 h 27	84	Strong coverage
October	18.2°C	5°C	21 mm	3.8	10 h 56	62	Strong coverage
November	9.3°C	-0.3°C	30 mm	6.9	9 h 36	21	Strong coverage
December	3.8°C	-3.8°C	39 mm	8.5	8 h 57	5	Strong coverage

What has changed

Boise runs +1.4°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

+1.5

Feb

+0.9

Mar

+1.6

Apr

+0.8

May

+0.9

Jun

+1.3

Jul

+2.6

Aug

+2.1

Sep

+2.4

Oct

+0.7

Nov

+0.7

Dec

+1.0

September daytime highs, 2011–2025. Last recorded: 28.8°C.

Records at BOISE AIR TERMINAL, 1940–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	18.9°C31 Jan 2024	-27.2°C31 Jan 1950	29 mm18 Jan 1953	99 mm1970 · driest 3 mm in 1949	87
February	21.7°C29 Feb 1992	-26.1°C5 Feb 1989	23 mm4 Feb 1951	95 mm2019 · driest 2 mm in 2022	87
March	28.3°C20 Mar 2026	-14.4°C1 Mar 1971	41 mm20 Mar 1981	88 mm1989 · driest 4 mm in 1994	87
April	33.3°C25 Apr 1946	-7.2°C13 Apr 1968	32 mm6 Apr 1969	98 mm2026 · driest 2 mm in 1949	87
May	37.8°C31 May 2025	-5.6°C5 May 1982	45 mm29 May 1990	112 mm1998 · driest 0 mm in 1992	87
June	43.3°C28 Jun 2015	-0.6°C7 Jun 1995	49 mm12 Jun 1958	87 mm1941 · driest 0 mm in 1960	87
July	43.9°C19 Jul 1960	1.7°C5 Jul 1986	24 mm30 Jul 1960	41 mm1982 · driest 0 mm in 1968	87
August	43.3°C4 Aug 1961	1.1°C24 Aug 1992	41 mm13 Aug 1979	71 mm2023 · driest 0 mm in 1955	86
September	40.0°C7 Sep 2022	-5.0°C14 Sep 1970	44 mm11 Sep 1976	75 mm1986 · driest 0 mm in 1993	86
October	34.4°C1 Oct 1992	-11.7°C29 Oct 1971	24 mm9 Oct 2018	66 mm2000 · driest 0 mm in 2003	86
November	25.6°C6 Nov 1999	-19.4°C15 Nov 1955	29 mm1 Nov 2014	86 mm1988 · driest 3 mm in 2019	86
December	18.3°C22 Dec 1964	-31.7°C22 Dec 1990	26 mm23 Dec 1955	108 mm1983 · driest 2 mm in 1976	86

Typical days per month at BOISE AIR TERMINAL, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	26	<1	5
February	0	0	20	<1	3
March	<1	0	11	<1	2
April	2	<1	5	<1	<1
May	11	3	<1	1	0
June	20	12	0	<1	0
July	30	26	0	<1	0
August	29	24	0	<1	0
September	20	10	<1	<1	0
October	4	<1	4	<1	<1
November	0	0	16	<1	2
December	0	0	25	<1	6

The best month has moved. On the 1961–1990 numbers the strongest month here was September (scoring 86); on 2011–2025 it is May (84). Both are scored the same way, from the same station — only the climate underneath changed.

How often, not how much — every day in BOISE AIR TERMINAL’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%	25%	2%	30%	-1.4–6.3°C
February	<1%	24%	1%	25%	3.6–10.3°C
March	7%	23%	2%	25%	9.2–14.5°C
April	26%	20%	2%	18%	14.5–19.3°C
May	58%	18%	3%	19%	19.4–24.7°C
June	81%	13%	2%	10%	23.7–29.7°C
July	96%	4%	<1%	<1%	30.8–36.2°C
August	95%	4%	<1%	2%	29.3–33.9°C
September	81%	9%	1%	6%	22.9–28.5°C
October	39%	13%	2%	12%	15.7–21.1°C
November	1%	24%	2%	28%	6.8–11.7°C
December	0%	26%	2%	29%	0.8–6.2°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.

1940Each stripe is one year’s mean temperature against the 86-year average. Warmest: 2025. Coolest: 1985.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 5586437
NOAA station: USW00024131 · BOISE AIR TERMINAL
Station distance: 6 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 30 usable years
Daylight: Calculated from latitude 43.61°, 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 BOISE AIR TERMINAL is what differs

Meridian→Kuna→Garden City→Ustick→Boise Hills Village→Boise Junction→

Or put two places side by side: Boise vs Meridian

Best time to visitBoise.

September

August

May

The whole year,without the guesswork.

Boise runs +1.4°Con the 1961–1990 baseline.

Nearby, measured,and named.

Best time to visit
Boise.

The whole year,
without the guesswork.

Boise runs +1.4°C
on the 1961–1990 baseline.

Nearby, measured,
and named.