Frost history / Rudyard 21 N, MT
Rudyard 21 N, MT: frost dates by year
Last spring and first fall frost at NOAA station USC00247248, 2001 to 2025, measured from daily minimum temperatures.
Elevation 3,000 ft, 48.854, -110.597. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 24 | Sep 11 |
| Earliest | Apr 26 (2018) | Aug 28 (2018) |
| Latest | Jun 18 (2004) | Oct 1 (2024) |
| Trend | 5.2 days earlier per decade | 0.7 days later per decade |
| Years with data | 22 | 20 |
At 28°F (hard freeze) the median last spring date is May 13 and the median first fall date is Sep 28.
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 22 | Sep 5 | May 7 | Oct 6 |
| 2024 | May 20 | Oct 1 | May 4 | Oct 3 |
| 2023 | Apr 29 | Sep 20 | Apr 23 | Oct 6 |
| 2022 | Jun 2 | Sep 10 | May 23 | Sep 21 |
| 2021 | May 23 | Sep 17 | May 22 | Sep 17 |
| 2020 | May 23 | Sep 8 | May 16 | Sep 28 |
| 2019 | May 28 | Sep 28 | May 10 | Sep 29 |
| 2018 | Apr 26 | Aug 28 | Apr 26 | Sep 28 |
| 2015 | May 29 | no data | May 29 | no data |
| 2014 | Jun 12 | Sep 11 | May 13 | Sep 12 |
| 2013 | May 21 | no data | May 11 | no data |
| 2012 | May 27 | Sep 7 | May 12 | Oct 4 |
| 2011 | May 18 | Sep 4 | May 11 | Sep 21 |
| 2010 | May 24 | Sep 12 | May 13 | Oct 14 |
| 2009 | Jun 10 | Sep 28 | May 21 | Sep 28 |
| 2008 | May 27 | Sep 24 | May 13 | Sep 24 |
| 2006 | May 14 | Sep 1 | May 4 | Sep 2 |
| 2005 | May 31 | Sep 6 | May 30 | Sep 24 |
| 2004 | Jun 18 | Sep 10 | May 14 | Oct 1 |
| 2003 | May 30 | Sep 14 | May 19 | Sep 18 |
| 2002 | May 24 | Sep 22 | May 24 | Sep 23 |
| 2001 | May 21 | Sep 16 | May 21 | Oct 3 |
"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.