Boise, ID

Idaho · Records since 1875–2026

☀️ 75°F Feels like 72°
Currently in Boise
As of 12:30 PM MDT

Records for September 11

🔥 Record High

97°F

September 11, 1963

+15° from 82° normal

❄ Record Low

27°F

September 11, 1889

-27° from 54° normal
🌞 Normal high: 82°F 🌑 Normal low: 54°F 1991–2020 normals

All-Time Records — Boise

🔥
111°F
Hottest Day Ever
Jul 19, 1960
❄
-28°F
Coldest Day Ever
Jan 16, 1888
🌧
2.46"
Wettest Day Ever
Mar 29, 1904
☃
15.5"
Most Snow in One Day
Feb 2, 1916

First & Last Dates — Boise

How early and how late each seasonal turning point has ever arrived, across the full period of record

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Range ever recorded Normal date (1991–2020)
232 days
Longest growing season
2016
97 days
Shortest growing season
1895
168 days
Normal growing season
1991–2020 average

Top 10 Record Highs — September 11

# Temp Date
🏆 97°F September 11, 1963
2 96°F September 11, 1953
3 96°F September 11, 1888
4 95°F September 11, 1996
5 95°F September 11, 1990
6 95°F September 11, 1959
7 94°F September 11, 2011
8 93°F September 11, 2023
9 93°F September 11, 1960
10 93°F September 11, 1940

Top 5 Record Lows — September 11

# Temp Date
🥶 27°F September 11, 1889
2 35°F September 11, 1982
3 36°F September 11, 1910
4 38°F September 11, 1906
5 38°F September 11, 1896
About this data — Records are sourced from the NOAA Threadex dataset via RCC ACIS, a quality-controlled record for long-term climate stations. Threadex adjusts for station relocations and observation-time changes, making records comparable across all years since 1875–2026. Climate normals represent the 1991–2020 average.

Heat Wave Summary — Boise

threshold: 98°F (90th percentile of historical Jun–Aug highs)
4.6
Avg heat wave length
days (historical)
104°
Avg peak temp
during heat waves
13
Dangerous nights 2026
Overnights ≥ 70°F
5
Heat waves 2026
so far

Days ≥ 90°F Per Year

1875–2026
58
2026 so far
45
Avg/year 1970–2025
62
Avg/year (last 10 complete)
76
Most in a year (1875)

Average Daily High by Decade

Full year · complete decades only

Longest Heat Waves — Boise

# Dates Days Peak Avg High Avg Overnight Low
🏆 Jul 8, 2024 – Jul 24, 2024 17 108°F (Jul 10) 104°F 72°F
2 Jun 27, 2021 – Jul 8, 2021 12 107°F (Jul 6) 102°F 73°F
3 Jul 12, 1960 – Jul 22, 1960 11 111°F (Jul 19) 102°F 66°F
4 Jul 19, 2006 – Jul 28, 2006 10 107°F (Jul 22) 102°F 70°F
5 Jul 23, 2018 – Aug 1, 2018 10 102°F (Jul 24) 100°F 68°F
6 Jun 26, 2015 – Jul 4, 2015 9 110°F (Jun 28) 103°F 71°F
7 Jul 19, 1931 – Jul 27, 1931 9 108°F (Jul 20) 102°F 68°F
8 Jul 15, 1998 – Jul 23, 1998 9 108°F (Jul 17) 100°F 65°F
9 Jul 15, 2003 – Jul 23, 2003 9 108°F (Jul 22) 103°F 68°F
10 Jul 21, 1994 – Jul 29, 1994 9 106°F (Jul 22) 101°F 68°F

Heat Waves Per Year

Warm Summer Nights (Jun–Aug)

Nights where the overnight low exceeded the 1991–2020 normal low

58
2026 total
above-normal nights
34.8
Avg / summer
1970–2020
68
Most in a summer
2022

Above-Normal Summer Nights Per Year

Average June–August Low by Decade

Overnight lows · complete decades only

Precipitation

Annual totals and trend across the full period of record · see this year's standing →

Monthly Precipitation — Last 24 Months

Blue = actual · dashed line = monthly normal

Annual Precipitation Per Year (1878–2026)

Blue = above average · tan = below average · gold = 2026 (partial)
Since 1878, annual totals have trended -0.10" per decade, about -1.5" across the record.

Heavy Rain Days Per Year (≥ 1.0")

Compare year-to-year changes in days with heavy rainfall (≥ 1.0")

This Year — 2026

How Boise is tracking against normal, year to date

Daily High Temperature vs Normal

Above normal Below normal

169 of 253 days with data were above the 1991–2020 normal high for their date.

Precipitation, Year to Date

7.81"
2026 YTD
Normal: 7.66"
+0.15"
0.31"
September so far
September normal: 0.43"
-0.12"
0
2026 heavy rain days
Days with ≥ 1.0"

Accumulation vs. Normal

Running total since Jan 1 against the normal pace for the same date · Boise is 0.15" ahead of the normal pace

Period Review — Mar 1 – May 31, 2026

Any window, evaluated against every other year on record — 92 days

Quick picks: Last 7 days Last 30 days Last 90 days This month
Seasons: Spring (Mar–May) Summer (Jun–Aug) Fall (Sep–Nov)
55.2°F
Average temperature
3rd-warmest of 149
+3.4°
vs. average
Normal: 51.8°F (1991–2020)
4.74"
Precipitation
41st-wettest of 149
+0.73"
vs. average
Normal: 4.01" · 118% of normal

Average Temperature by Year — Mar 1 – May 31

1878–2026 · 2026 highlighted · trend +0.11° per decade (warming since 1878)

Precipitation by Year — Mar 1 – May 31

1878–2026 · 2026 highlighted

Warmest Mar 1 – May 31 on Record

# Year Avg Temp
1 1934 57.9°F
2 1992 56.0°F
3 2026 55.2°F
4 2016 54.9°F
5 1910 54.9°F
6 1889 54.7°F
7 2015 54.3°F
8 2007 54.2°F
9 1987 54.1°F
10 2025 53.8°F

Coolest Mar 1 – May 31 on Record

# Year Avg Temp
1 1955 44.6°F
2 1917 44.9°F
3 1896 45.3°F
4 1964 46.0°F
5 1922 46.7°F
6 1893 46.7°F
7 1953 46.9°F
8 1920 47.1°F
9 1950 47.1°F
10 1982 47.1°F

Wettest Mar 1 – May 31 on Record

# Year Total
1 1896 10.05"
2 2019 7.28"
3 1980 7.11"
4 1990 6.98"
5 1917 6.94"
6 1983 6.92"
7 1938 6.80"
8 1904 6.73"
9 1932 6.60"
10 1912 6.54"

Driest Mar 1 – May 31 on Record

# Year Total
1 1992 0.83"
2 1924 0.89"
3 1939 1.23"
4 1949 1.30"
5 1934 1.44"
6 1968 1.46"
7 1966 1.53"
8 1888 1.57"
9 2007 1.62"
10 1909 1.79"
About this data. Pick any start and end date and this becomes the same kind of review as the Month and Fall tabs, just for exactly the window you asked for — the generalized version of the same engine, evaluated across every year on record. Average temperature is the mean of each day's (high + low) / 2; precipitation is the sum of daily totals. A year missing more than about a fifth of the window's days is excluded from the temperature ranking; any missing day excludes a year from the precipitation ranking, since an unreported day is unreported rain. Ranges that cross from December into January aren't supported yet. Normals are the 1991–2020 mean for the same window.
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