Frost history / Thermopolis 9NE, WY
Thermopolis 9NE, WY: frost dates by year
Last spring and first fall frost at NOAA station USC00488884, 2006 to 2025, measured from daily minimum temperatures.
Elevation 4,282 ft, 43.753, -108.143. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 22 | Sep 18 |
| Earliest | May 4 (2018) | Sep 4 (2010) |
| Latest | Jun 20 (2024) | Oct 6 (2025) |
| Trend | little change (less than half a day per decade) | 5.7 days later per decade |
| Years with data | 19 | 18 |
At 28°F (hard freeze) the median last spring date is May 9 and the median first fall date is Oct 1.
The trend is a straight-line fit through the years with a freeze. A positive spring trend means the last frost now comes later. Short or patchy records give noisy trends.
Chart
Last spring frost (32°F)
First fall frost (32°F)
Dots are single years. The gray line is the median, the green line the fitted trend.
Year by year
| Year | Last spring 32°F | First fall 32°F | Last spring 28°F | First fall 28°F |
|---|---|---|---|---|
| 2025 | May 20 | Oct 6 | May 4 | Oct 7 |
| 2024 | Jun 20 | Sep 22 | May 24 | Oct 1 |
| 2023 | May 10 | Sep 25 | Apr 29 | Sep 26 |
| 2022 | Jun 15 | Sep 11 | Jun 15 | Oct 12 |
| 2021 | May 12 | Sep 21 | May 9 | Sep 30 |
| 2020 | May 9 | Sep 8 | May 9 | Sep 10 |
| 2019 | Jun 9 | Sep 18 | May 10 | Oct 3 |
| 2018 | May 4 | Sep 21 | Apr 28 | Sep 26 |
| 2017 | May 27 | Sep 18 | Apr 30 | Oct 4 |
| 2016 | May 24 | Sep 10 | May 3 | Oct 8 |
| 2015 | May 22 | Sep 8 | May 12 | Oct 13 |
| 2014 | May 15 | Sep 12 | May 14 | Sep 12 |
| 2013 | May 31 | Sep 21 | May 4 | Sep 28 |
| 2012 | May 15 | Sep 13 | May 9 | Sep 14 |
| 2011 | May 31 | Sep 18 | May 6 | Sep 21 |
| 2010 | May 16 | Sep 4 | May 9 | Oct 14 |
| 2009 | May 21 | no data | May 17 | no data |
| 2008 | Jun 13 | no data | May 4 | no data |
| 2007 | May 26 | Sep 10 | May 7 | Sep 11 |
| 2006 | no data | Sep 24 | no data | Oct 13 |
"none" means the station recorded no freeze at that threshold in that half of the year. "no data" means more than 10% of the season's daily readings were missing. Years with no usable data are left out. See the methodology for the rules, and the ZIP lookup for 1991 to 2020 frost probabilities.