Frost history / Lewistown 42 Wsw, MT
Lewistown 42 Wsw, MT: frost dates by year
Last spring and first fall frost at NOAA station USW00004140, 2008 to 2024, measured from daily minimum temperatures.
Elevation 5,070 ft, 46.885, -110.289. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | Jun 21 | Sep 3 |
| Earliest | May 25 (2015) | Aug 14 (2020) |
| Latest | Jul 20 (2019) | Sep 22 (2024) |
| Trend | 8.6 days later per decade | 5.1 days later per decade |
| Years with data | 16 | 17 |
At 28°F (hard freeze) the median last spring date is May 29 and the median first fall date is Sep 13.
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 |
|---|---|---|---|---|
| 2024 | Jun 29 | Sep 22 | Jun 13 | Sep 30 |
| 2023 | Jun 22 | Sep 15 | Jun 22 | Sep 20 |
| 2022 | Jun 26 | Sep 9 | Jun 26 | Sep 9 |
| 2021 | Jun 21 | Aug 29 | May 30 | Sep 16 |
| 2020 | Jun 5 | Aug 14 | May 15 | Sep 8 |
| 2019 | Jul 20 | Sep 12 | May 29 | Sep 28 |
| 2018 | Jul 4 | Aug 28 | May 2 | Aug 28 |
| 2017 | Jun 30 | Sep 5 | Jun 23 | Sep 24 |
| 2016 | Jun 20 | Aug 25 | May 12 | Sep 13 |
| 2015 | May 25 | Aug 19 | May 21 | Aug 22 |
| 2014 | Jun 12 | Sep 5 | May 14 | Sep 5 |
| 2013 | Jun 5 | Sep 19 | Jun 5 | Sep 27 |
| 2012 | Jun 16 | Aug 25 | May 29 | Aug 25 |
| 2011 | Jun 15 | Sep 3 | May 19 | Sep 3 |
| 2010 | Jul 4 | Aug 24 | May 22 | Oct 15 |
| 2009 | Jun 12 | Sep 9 | Jun 8 | Sep 27 |
| 2008 | no data | Sep 2 | no data | Sep 5 |
"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.