When to plant in Colstrip, MT

Planting dates worked out from Colstrip's own frost records, not a generic zone chart.

Safe to plant out

May 24

1 year in 10 has a later frost

Average last frost

May 14

about a 50% chance of a later one

Average first fall frost

Sep 29

1 year in 10 by Sep 13

Frost-free days

134

median, 1991–2020

Station used: Colstrip · 1.4 km away · station 981 m, town 982 m. How we match towns to stations

This season

Plan your garden.

Build my Colstrip plan

Planting dates for common crops

Crop	Start indoors	Plant out or sow	Harvest from
Tomato	Mar 29 – Apr 12	May 24 – Jun 7	Jul 18
Sweet pepper	Mar 15 – Mar 29	May 24 – Jun 7	Jul 23
Lettuce (leaf)	Mar 12 – Mar 19	Apr 16 – Apr 30	May 26
Peas	—	Apr 11 – May 9	Jun 5
Bush beans	—	May 17 – Jun 7	Jul 6
Carrot	—	Apr 24 – Jun 5	Jun 23
Beet	—	Apr 24 – Jun 5	Jun 13
Potato	—	Apr 24 – May 15	Jul 3
Kale	Mar 7 – Mar 21	Apr 18 – May 2	May 31
Broccoli	Mar 5 – Mar 19	Apr 16 – May 7	Jun 15
Cucumber	Apr 26 – May 3	May 24 – Jun 7	Jul 13
Summer squash and zucchini	Apr 26 – May 3	May 24 – Jun 7	Jul 8
Winter squash	Apr 26 – May 3	May 24 – Jun 7	Aug 12
Sweet corn	—	May 17 – Jun 7	Jul 16
Onion (from sets)	—	Apr 16 – May 7	Jul 15
Garlic	—	Sep 15 – Oct 13 (fall)	following summer
Spinach	—	Apr 11 – May 9	May 19
Basil	Apr 12 – Apr 26	May 24 – Jun 7	Jul 20

Plan all 65 crops for Colstrip

Colstrip's weather over time

How the growing season has shifted here, year by year, from the station's own records.

Each year's last spring frostLong-term trend

See the data as a table

Year	Last spring frost
1927	May 19
1928	Jun 1
1929	May 19
1930	May 16
1931	May 22
1932	May 27
1933	Apr 22
1934	May 22
1935	May 28
1936	May 8
1937	May 16
1938	Jun 11
1939	May 22
1940	May 14
1941	May 10
1942	May 19
1943	Jun 6
1945	May 22
1946	May 18
1947	May 29
1948	May 17
1949	May 24
1950	Jun 8
1951	Jun 2
1952	May 10
1953	May 25
1954	May 31
1955	Jun 8
1956	May 14
1957	Apr 26
1958	May 19
1959	May 29
1960	May 20
1961	May 8
1962	May 1
1963	May 22
1964	Jun 2
1965	Jun 8
1966	May 12
1967	May 14
1968	May 20
1969	Jun 15
1970	Jun 13
1971	May 19
1972	May 11
1974	May 23
1976	May 7
1977	Apr 25
1978	Apr 24
1979	May 11
1982	Jun 1
1983	Jun 4
1984	Jun 8
1985	May 13
1986	May 16
1987	May 20
1988	May 2
1989	May 25
1990	May 16
1991	May 4
1992	May 15
1993	May 23
1994	Apr 29
1995	May 13
1996	May 10
1998	May 9
1999	May 22
2000	May 12
2001	May 6
2002	May 23
2003	May 19
2004	May 24
2005	May 14
2006	May 11
2007	Apr 13
2009	Jun 8
2010	May 8
2011	May 2
2012	May 11
2013	May 24
2014	May 19
2015	May 20
2016	May 22
2017	May 30
2018	Apr 30
2019	May 25
2020	May 5
2021	May 28
2022	May 22
2024	Apr 21
2026	May 5

Each year's frost-free daysLong-term trend

See the data as a table

Year	Frost-free days
1927	123
1929	110
1930	126
1931	123
1932	116
1933	156
1934	114
1935	98
1936	130
1937	131
1938	124
1939	125
1940	118
1941	126
1942	121
1945	110
1946	132
1947	108
1948	137
1949	110
1950	112
1951	104
1952	134
1953	118
1954	112
1955	94
1958	119
1959	121
1960	110
1961	117
1962	125
1963	151
1964	96
1965	90
1966	144
1967	135
1968	124
1969	92
1970	90
1971	121
1972	132
1977	151
1978	147
1982	104
1983	105
1984	105
1985	131
1986	146
1987	136
1988	154
1989	107
1990	141
1991	135
1992	120
1993	111
1994	160
1995	129
1996	138
1998	135
1999	130
2000	131
2001	150
2002	131
2003	120
2004	129
2005	143
2006	152
2007	196
2009	111
2010	157
2011	141
2012	145
2013	132
2014	115
2015	147
2016	136
2017	118
2018	156
2019	128
2020	125
2021	111
2022	146
2024	185

Each year's average temperature, April to SeptemberLong-term trend

See the data as a table

Year	Growing-season temperature
1927	14.0 °C
1928	14.8 °C
1929	15.8 °C
1930	17.5 °C
1931	17.5 °C
1932	16.9 °C
1933	16.8 °C
1934	17.2 °C
1935	15.5 °C
1936	18.8 °C
1937	17.5 °C
1938	16.3 °C
1939	17.0 °C
1940	17.1 °C
1941	15.8 °C
1942	15.1 °C
1945	14.5 °C
1946	15.9 °C
1947	15.7 °C
1948	16.8 °C
1949	16.4 °C
1950	14.0 °C
1951	14.0 °C
1952	17.0 °C
1953	15.4 °C
1954	15.7 °C
1955	16.3 °C
1956	16.0 °C
1957	16.4 °C
1958	16.4 °C
1959	15.8 °C
1960	16.9 °C
1961	16.9 °C
1962	16.1 °C
1963	16.8 °C
1964	15.6 °C
1965	14.4 °C
1966	16.7 °C
1967	15.7 °C
1968	15.2 °C
1969	16.6 °C
1970	15.8 °C
1971	16.6 °C
1972	15.9 °C
1976	17.2 °C
1977	16.8 °C
1978	15.9 °C
1979	16.1 °C
1982	14.5 °C
1983	15.7 °C
1984	15.5 °C
1985	15.7 °C
1986	15.4 °C
1987	16.6 °C
1988	18.0 °C
1989	16.1 °C
1990	16.3 °C
1991	16.1 °C
1992	15.1 °C
1993	14.1 °C
1994	16.6 °C
1995	14.6 °C
1996	15.7 °C
1998	17.1 °C
1999	15.3 °C
2000	16.6 °C
2001	16.8 °C
2002	16.1 °C
2003	15.1 °C
2004	15.6 °C
2005	15.7 °C
2006	16.9 °C
2007	16.6 °C
2009	15.3 °C
2010	15.0 °C
2011	15.2 °C
2012	17.4 °C
2013	15.8 °C
2014	15.3 °C
2015	16.6 °C
2016	16.3 °C
2017	16.5 °C
2018	15.3 °C
2019	14.7 °C
2020	16.1 °C
2021	16.4 °C
2022	16.8 °C
2024	18.0 °C

What this means for you: Since 1927, Colstrip's last spring frost has come about 1 day earlier per decade, on average. The frost-free season has grown by about 3 days per decade. Year-to-year swings are large, so keep using the safe date rather than the trend.

Source: daily records from Colstrip (NOAA GHCN-Daily). Years with too many missing days are left out.

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