Casper, WY

Wyoming · Records since 1939–2026

☀️ 80°F Feels like 70°
Currently in Casper
As of 12:30 PM MDT

Records for September 11

🔥 Record High

91°F

September 11, 1993

+13° from 78° normal

❄ Record Low

26°F

September 11, 2014

-18° from 44° normal
🌞 Normal high: 78°F 🌑 Normal low: 44°F 1991–2020 normals

All-Time Records — Casper

🔥
104°F
Hottest Day Ever
Jul 29, 2006
❄
-42°F
Coldest Day Ever
Dec 22, 2022
🌧
2.80"
Wettest Day Ever
Apr 13, 1941
☃
26.7"
Most Snow in One Day
Apr 3, 2023

First & Last Dates — Casper

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)
165 days
Longest growing season
1963
34 days
Shortest growing season
1972
118 days
Normal growing season
1991–2020 average

Top 10 Record Highs — September 11

# Temp Date
🏆 91°F September 11, 1993
2 90°F September 11, 1971
3 89°F September 11, 2025
4 89°F September 11, 2017
5 89°F September 11, 1990
6 89°F September 11, 1959
7 89°F September 11, 1954
8 88°F September 11, 1968
9 87°F September 11, 2021
10 87°F September 11, 2004

Top 5 Record Lows — September 11

# Temp Date
🥶 26°F September 11, 2014
2 27°F September 11, 1989
3 32°F September 11, 2007
4 33°F September 11, 1974
5 34°F September 11, 1950
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 1939–2026. Climate normals represent the 1991–2020 average.

Heat Wave Summary — Casper

threshold: 94°F (90th percentile of historical Jun–Aug highs)
4.1
Avg heat wave length
days (historical)
98°
Avg peak temp
during heat waves
0
Dangerous nights 2026
Overnights ≥ 70°F
5
Heat waves 2026
so far

Days ≥ 90°F Per Year

1940–2026
50
2026 so far
32
Avg/year 1970–2025
42
Avg/year (last 10 complete)
57
Most in a year (1988)

Average Daily High by Decade

Full year · complete decades only

Longest Heat Waves — Casper

# Dates Days Peak Avg High Avg Overnight Low
🏆 Jul 10, 2026 – Jul 20, 2026 11 103°F (Jul 12) 98°F 57°F
2 Jul 15, 2007 – Jul 25, 2007 11 99°F (Jul 17) 96°F 59°F
3 Jun 23, 1990 – Jul 2, 1990 10 102°F (Jun 30) 99°F 57°F
4 Jun 25, 2002 – Jul 3, 2002 9 100°F (Jun 30) 96°F 53°F
5 Aug 6, 2003 – Aug 14, 2003 9 99°F (Aug 14) 97°F 60°F
6 Jun 20, 1988 – Jun 27, 1988 8 102°F (Jun 24) 98°F 65°F
7 Jul 3, 1989 – Jul 9, 1989 7 102°F (Jul 8) 98°F 58°F
8 Aug 2, 2001 – Aug 8, 2001 7 101°F (Aug 6) 97°F 62°F
9 Jul 19, 2014 – Jul 25, 2014 7 100°F (Jul 23) 96°F 55°F
10 Jul 19, 2005 – Jul 24, 2005 6 103°F (Jul 22) 98°F 58°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
47.3
Avg / summer
1970–2020
77
Most in a summer
1961

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 (1939–2026)

Blue = above average · tan = below average · gold = 2026 (partial)
Since 1939, annual totals have trended +0.27" per decade, about +2.3" 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 Casper is tracking against normal, year to date

Daily High Temperature vs Normal

Above normal Below normal

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

Precipitation, Year to Date

6.35"
2026 YTD
Normal: 9.07"
-2.72"
0.01"
September so far
September normal: 0.95"
-0.94"
1
2026 heavy rain days
Days with ≥ 1.0"

Accumulation vs. Normal

Running total since Jan 1 against the normal pace for the same date · Casper is 2.72" behind the normal pace

Period Review — Sep 1 – Sep 10, 2026

Any window, evaluated against every other year on record — 10 days

Quick picks: Last 7 days Last 30 days Last 90 days This month
Seasons: Spring (Mar–May) Summer (Jun–Aug) Fall (Sep–Nov)
67.8°F
Average temperature
16th-warmest of 87
+4.0°
vs. average
Normal: 63.8°F (1991–2020)
0.01"
Precipitation
13th-driest of 87
-0.22"
vs. average
Normal: 0.23" · 4% of normal

Average Temperature by Year — Sep 1 – Sep 10

1940–2026 · 2026 highlighted · trend +0.18° per decade (warming since 1940)

Precipitation by Year — Sep 1 – Sep 10

1940–2026 · 2026 highlighted · trend -0.01" per decade (drier since 1940)

Warmest Sep 1 – Sep 10 on Record

# Year Avg Temp
1 1998 73.1°F
2 1978 72.1°F
3 2013 71.7°F
4 1990 70.2°F
5 1940 69.8°F
6 1983 69.2°F
7 1955 69.1°F
8 1947 68.6°F
9 1952 68.5°F
10 1982 68.5°F

Coolest Sep 1 – Sep 10 on Record

# Year Avg Temp
1 2008 52.5°F
2 1943 55.3°F
3 1962 55.3°F
4 2020 55.3°F
5 2006 57.1°F
6 1941 57.3°F
7 1965 57.3°F
8 1961 57.5°F
9 1989 58.0°F
10 1968 58.1°F

Wettest Sep 1 – Sep 10 on Record

# Year Total
1 1973 2.29"
2 1989 1.06"
3 1943 0.88"
4 1999 0.81"
5 1946 0.79"
6 1951 0.79"
7 1993 0.66"
8 1986 0.63"
9 2004 0.62"
10 2016 0.56"

Driest Sep 1 – Sep 10 on Record

# Year Total
1 2018 0.00"
2 2017 0.00"
3 2011 0.00"
4 2009 0.00"
5 1980 0.00"
6 1977 0.00"
7 1975 0.00"
8 1969 0.00"
9 1959 0.00"
10 1956 0.00"
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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