Last Frost Day

Frost history / Port Of Morgan, MT

Port Of Morgan, MT: frost dates by year

Last spring and first fall frost at NOAA station USC00246672, 1976 to 2025, measured from daily minimum temperatures.

Elevation 2,830 ft, 48.998, -107.833. Download the data (JSON), NOAA daily records

Summary at 32°F

Last spring frostFirst fall frost
MedianMay 16Sep 17
EarliestApr 28 (2023)Aug 2 (1978)
LatestJun 20 (1978)Oct 6 (2025)
Trend2.8 days earlier per decade3.5 days later per decade
Years with data3626

At 28°F (hard freeze) the median last spring date is May 10 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)

Apr 15Apr 30May 15May 30Jun 14Jun 29198019902000201020201977: May 61978: Jun 201979: Jun 11981: Jun 151982: May 311983: May 131987: May 201989: May 51990: Jun 31991: May 51992: May 291995: May 271996: May 121997: May 111999: May 122000: May 132001: May 212002: May 242004: May 162005: May 142006: May 122007: Jun 162008: May 132009: Jun 82010: May 302011: May 112012: May 292013: May 112014: May 172015: May 292020: May 162021: May 222022: May 232023: Apr 282024: May 22025: May 7

First fall frost (32°F)

Jul 14Jul 29Aug 13Aug 28Sep 12Sep 27Oct 12198019902000201020201976: Sep 191978: Aug 21980: Sep 161985: Sep 81986: Oct 31988: Sep 191989: Sep 101990: Sep 221991: Sep 171992: Sep 61995: Sep 191999: Sep 192000: Sep 112005: Sep 282006: Sep 172007: Sep 132009: Sep 282011: Sep 142012: Sep 122013: Sep 272014: Sep 112019: Sep 282020: Sep 82021: Sep 172024: Oct 32025: 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 7Oct 6Apr 23Oct 6
2024May 2Oct 3Apr 23Oct 3
2023Apr 28no dataApr 21no data
2022May 23no dataMay 23no data
2021May 22Sep 17May 21Oct 11
2020May 16Sep 8May 11Sep 8
2019no dataSep 28no dataSep 28
2015May 29no dataMay 10no data
2014May 17Sep 11May 14Oct 3
2013May 11Sep 27May 11Oct 4
2012May 29Sep 12May 11Oct 5
2011May 11Sep 14May 9Oct 14
2010May 30no dataMay 10no data
2009Jun 8Sep 28May 13Sep 28
2008May 13no dataMay 10no data
2007Jun 16Sep 13Apr 23Sep 14
2006May 12Sep 17Apr 26Oct 8
2005May 14Sep 28May 14Sep 28
2004May 16no dataMay 14no data
2002May 24no dataMay 23no data
2001May 21no dataMay 21no data
2000May 13Sep 11May 12Sep 22
1999May 12Sep 19May 6Sep 19
1997May 11no dataMay 8no data
1996May 12no dataMay 10no data
1995May 27Sep 19May 13Sep 19
1992May 29Sep 6May 22Sep 18
1991May 5Sep 17May 5Sep 18
1990Jun 3Sep 22May 15Oct 4
1989May 5Sep 10May 5Sep 11
1988no dataSep 19no dataOct 4
1987May 20no dataApr 21no data
1986no dataOct 3no dataOct 11
1985no dataSep 8no dataSep 20
1983May 13no dataMay 13no data
1982May 31no dataMay 31no data
1981Jun 15no dataApr 19no data
1980no dataSep 16no dataSep 24
1979Jun 1no dataMay 20no data
1978Jun 20Aug 2Apr 20Sep 20
1977May 6no dataMay 1no data
1976no dataSep 19no dataSep 19

"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.