Last Frost Day

Frost history / Trout Creek Rs, MT

Trout Creek Rs, MT: frost dates by year

Last spring and first fall frost at NOAA station USC00248380, 1960 to 2025, measured from daily minimum temperatures.

Elevation 2,356 ft, 47.867, -115.628. Download the data (JSON), NOAA daily records

Summary at 32°F

Last spring frostFirst fall frost
MedianJun 4Sep 12
EarliestMay 3 (1993)Aug 13 (1982)
LatestJul 23 (1963)Oct 13 (2008)
Trend6.0 days earlier per decade5.1 days later per decade
Years with data4953

At 28°F (hard freeze) the median last spring date is May 16 and the median first fall date is Sep 23.

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)

Apr 15Apr 30May 15May 30Jun 14Jun 29Jul 14Jul 2919601970198019902000201020201961: Jun 81962: Jul 31963: Jul 231964: Jun 291965: Jun 291966: May 241967: Jun 51968: Jun 41969: Jun 141970: May 191971: Jul 71972: May 311973: Jun 111974: Jun 11975: Jun 301976: Jul 31977: Jul 71979: Jul 31980: Jun 41981: May 141982: May 311983: Jul 151984: Jun 261985: Jun 251986: Jun 131987: Jun 171988: May 211989: May 211990: Jun 51991: Jun 181993: May 31994: Jun 21995: May 231996: Jun 201997: May 221998: Jun 41999: Jul 192000: May 312001: May 302002: May 152003: May 202004: May 242007: May 62008: Jun 172009: Jun 82010: May 242011: May 192013: May 252025: May 6

First fall frost (32°F)

Jul 29Aug 13Aug 28Sep 12Sep 27Oct 12Oct 2719601970198019902000201020201960: Sep 61961: Sep 71962: Aug 301963: Sep 191965: Aug 251966: Sep 11967: Sep 231968: Sep 81969: Aug 171970: Sep 101971: Sep 131972: Aug 311973: Aug 181974: Sep 21975: Sep 11976: Sep 71977: Sep 21978: Sep 161979: Sep 121980: Aug 291981: Sep 231982: Aug 131983: Sep 191984: Sep 141985: Aug 161986: Sep 121987: Aug 161988: Sep 121989: Sep 91990: Oct 11991: Sep 221992: Aug 241993: Sep 221994: Oct 41995: Sep 211996: Sep 231997: Oct 61998: Oct 41999: Sep 12000: Sep 222001: Sep 82002: Sep 212003: Oct 102004: Oct 112005: Sep 202006: Sep 152007: Sep 92008: Oct 132009: Sep 212010: Oct 122011: Sep 32012: Sep 132025: Oct 6

Dots are single years. The gray line is the median, the green line the fitted trend.

Year by year

YearLast spring 32°FFirst fall 32°FLast spring 28°FFirst fall 28°F
2025May 6Oct 6May 6Oct 15
2013May 25no dataApr 28no data
2012no dataSep 13no dataSep 13
2011May 19Sep 3May 2Oct 25
2010May 24Oct 12May 24Oct 16
2009Jun 8Sep 21Apr 19Oct 9
2008Jun 17Oct 13May 3Oct 15
2007May 6Sep 9May 6Sep 29
2006no dataSep 15no dataSep 15
2005no dataSep 20no dataNov 9
2004May 24Oct 11Apr 25Oct 26
2003May 20Oct 10May 17Oct 24
2002May 15Sep 21May 12Oct 2
2001May 30Sep 8May 21Oct 5
2000May 31Sep 22May 14Sep 23
1999Jul 19Sep 1Jun 10Sep 3
1998Jun 4Oct 4May 16Oct 16
1997May 22Oct 6May 8Oct 25
1996Jun 20Sep 23May 10Sep 24
1995May 23Sep 21Apr 17Sep 21
1994Jun 2Oct 4Apr 29Nov 13
1993May 3Sep 22Apr 20Oct 10
1992no dataAug 24no dataSep 18
1991Jun 18Sep 22May 2Sep 22
1990Jun 5Oct 1May 9Oct 7
1989May 21Sep 9May 21Oct 3
1988May 21Sep 12May 1Sep 12
1987Jun 17Aug 16May 22Sep 19
1986Jun 13Sep 12Jun 13Sep 12
1985Jun 25Aug 16May 13Sep 23
1984Jun 26Sep 14May 17Sep 24
1983Jul 15Sep 19May 14Sep 19
1982May 31Aug 13May 20Sep 15
1981May 14Sep 23May 5Sep 23
1980Jun 4Aug 29May 11Sep 24
1979Jul 3Sep 12Jul 3Sep 29
1978no dataSep 16no dataSep 16
1977Jul 7Sep 2May 16Sep 9
1976Jul 3Sep 7May 29Sep 7
1975Jun 30Sep 1May 26Sep 22
1974Jun 1Sep 2May 17Sep 12
1973Jun 11Aug 18May 22Aug 19
1972May 31Aug 31May 19Sep 10
1971Jul 7Sep 13May 22Sep 14
1970May 19Sep 10May 18Sep 13
1969Jun 14Aug 17May 8Sep 15
1968Jun 4Sep 8May 12Oct 3
1967Jun 5Sep 23May 26Oct 20
1966May 24Sep 1May 22Oct 9
1965Jun 29Aug 25May 18Aug 25
1964Jun 29no dataJun 28no data
1963Jul 23Sep 19May 20Oct 20
1962Jul 3Aug 30May 31Sep 8
1961Jun 8Sep 7May 11Sep 13
1960no dataSep 6no dataSep 21

"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.