Frost history / Rustic 9WSW, CO
Rustic 9WSW, CO: frost dates by year
Last spring and first fall frost at NOAA station USC00057296, 1993 to 2025, measured from daily minimum temperatures.
Elevation 7,700 ft, 40.702, -105.711. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | Jun 2 | Sep 19 |
| Earliest | May 19 (1997) | Sep 2 (2006) |
| Latest | Jun 19 (2010) | Oct 7 (2023) |
| Trend | 2.0 days earlier per decade | 2.6 days later per decade |
| Years with data | 31 | 30 |
At 28°F (hard freeze) the median last spring date is May 21 and the median first fall date is Sep 24.
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 | no data | May 22 | no data |
| 2024 | May 25 | Sep 20 | May 9 | Oct 19 |
| 2023 | May 20 | Oct 7 | May 2 | Oct 13 |
| 2022 | Jun 2 | Oct 7 | May 23 | Oct 7 |
| 2021 | May 25 | Sep 21 | May 25 | Oct 13 |
| 2020 | May 26 | no data | May 17 | no data |
| 2019 | Jun 10 | Sep 22 | May 22 | Oct 3 |
| 2018 | Jun 12 | Sep 21 | May 1 | Sep 26 |
| 2017 | May 29 | Sep 17 | May 22 | Sep 17 |
| 2016 | May 27 | Sep 10 | May 23 | Sep 10 |
| 2015 | May 24 | Sep 19 | May 20 | Oct 16 |
| 2014 | Jun 9 | Sep 12 | May 15 | Sep 12 |
| 2013 | Jun 5 | Sep 20 | Jun 2 | Oct 4 |
| 2012 | May 30 | Oct 4 | May 12 | Oct 5 |
| 2011 | Jun 9 | Sep 4 | May 16 | Oct 20 |
| 2010 | Jun 19 | Sep 7 | May 31 | Sep 7 |
| 2009 | no data | Sep 21 | no data | Sep 28 |
| 2008 | Jun 12 | Sep 3 | May 23 | Sep 3 |
| 2007 | Jun 9 | Sep 19 | Jun 8 | Sep 25 |
| 2006 | May 31 | Sep 2 | May 30 | Sep 21 |
| 2005 | Jun 12 | Sep 13 | May 28 | Sep 18 |
| 2004 | Jun 13 | Sep 6 | May 15 | Sep 22 |
| 2003 | Jun 7 | Sep 14 | May 12 | Sep 19 |
| 2002 | May 28 | Sep 22 | May 25 | Sep 22 |
| 2001 | Jun 6 | Sep 8 | May 21 | Oct 4 |
| 2000 | Jun 18 | Sep 20 | May 14 | Sep 23 |
| 1999 | May 22 | Sep 5 | May 17 | Sep 13 |
| 1998 | Jun 6 | no data | May 23 | no data |
| 1997 | May 19 | Oct 7 | May 11 | Oct 9 |
| 1996 | May 31 | Sep 18 | May 21 | Sep 26 |
| 1995 | Jun 11 | Sep 21 | May 24 | Sep 21 |
| 1994 | May 22 | Sep 22 | May 1 | Sep 22 |
| 1993 | no data | Sep 13 | no data | Sep 14 |
"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.