When to plant in Great Falls, MT

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

Safe to plant out

Jun 4

1 year in 10 has a later frost

Average last frost

May 19

about a 50% chance of a later one

Average first fall frost

Sep 20

1 year in 10 by Sep 11

Frost-free days

124

median, 1991–2020

Station used: Great Falls Ap · 6.9 km away · station 1118 m, town 1015 m. How we match towns to stations

This season

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Planting dates for common crops

Crop	Start indoors	Plant out or sow	Harvest from
Tomato	Apr 9 – Apr 23	Jun 4 – Jun 18	Jul 29
Sweet pepper	Mar 26 – Apr 9	Jun 4 – Jun 18	Aug 3
Lettuce (leaf)	Mar 17 – Mar 24	Apr 21 – May 5	May 31
Peas	—	Apr 17 – May 15	Jun 11
Bush beans	—	May 28 – Jun 18	Jul 17
Carrot	—	Apr 29 – Jun 10	Jun 28
Beet	—	Apr 29 – Jun 10	Jun 18
Potato	—	Apr 29 – May 20	Jul 8
Kale	Mar 13 – Mar 27	Apr 24 – May 8	Jun 6
Broccoli	Mar 10 – Mar 24	Apr 21 – May 12	Jun 20
Cucumber	May 7 – May 14	Jun 4 – Jun 18	Jul 24
Summer squash and zucchini	May 7 – May 14	Jun 4 – Jun 18	Jul 19
Winter squash	May 7 – May 14	Jun 4 – Jun 18	Aug 23
Sweet corn	—	May 28 – Jun 18	Jul 27
Onion (from sets)	—	Apr 21 – May 12	Jul 20
Garlic	—	Sep 6 – Oct 4 (fall)	following summer
Spinach	—	Apr 17 – May 15	May 25
Basil	Apr 23 – May 7	Jun 4 – Jun 18	Jul 31

Plan all 65 crops for Great Falls

Great Falls'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
1938	May 8
1939	May 1
1940	Apr 26
1941	Apr 19
1942	May 17
1943	May 15
1944	May 3
1945	May 9
1946	May 14
1947	May 28
1948	May 9
1949	May 23
1950	Jun 8
1951	Jun 7
1952	Apr 21
1953	May 13
1954	May 7
1955	May 16
1956	May 6
1957	Apr 25
1958	Apr 28
1959	May 20
1960	May 6
1961	May 12
1962	Apr 30
1963	May 22
1964	Apr 28
1965	May 18
1966	May 12
1967	May 13
1968	May 19
1969	Jun 13
1970	May 13
1971	Apr 27
1972	May 10
1973	May 11
1974	May 16
1975	May 26
1976	May 15
1977	May 18
1978	May 8
1979	May 10
1980	May 12
1981	May 5
1982	May 31
1983	May 16
1984	Jun 2
1985	May 16
1986	May 1
1987	May 22
1988	May 3
1989	May 29
1990	May 19
1991	May 5
1992	May 22
1993	Apr 28
1994	Apr 30
1995	May 27
1996	May 21
1997	May 19
1998	Jun 4
1999	Jun 10
2000	May 31
2001	May 21
2002	May 23
2003	May 19
2004	May 25
2005	May 27
2006	May 10
2007	May 24
2008	Jun 11
2009	Jun 8
2010	May 21
2011	May 2
2012	May 28
2013	May 8
2014	May 13
2015	May 18
2016	May 11
2017	May 3
2018	May 2
2019	May 18
2020	May 23
2021	May 22
2022	May 31
2023	Apr 23
2024	May 31

Each year's frost-free daysLong-term trend

See the data as a table

Year	Frost-free days
1938	158
1939	149
1940	184
1941	157
1942	157
1943	125
1944	148
1945	135
1946	144
1947	111
1948	149
1949	109
1950	112
1951	108
1952	165
1953	161
1954	143
1955	130
1956	121
1957	145
1958	162
1959	132
1960	159
1961	123
1962	129
1963	150
1964	157
1965	119
1966	140
1967	163
1968	123
1969	115
1970	120
1971	146
1972	135
1973	125
1974	135
1975	115
1976	152
1977	130
1978	131
1979	145
1980	134
1981	140
1982	104
1983	124
1984	102
1985	128
1986	161
1987	138
1988	130
1989	102
1990	131
1991	135
1992	91
1993	145
1994	154
1995	114
1996	123
1997	122
1998	120
1999	93
2000	112
2001	133
2002	124
2003	119
2004	128
2005	106
2006	128
2007	111
2008	118
2009	104
2010	118
2011	140
2012	128
2013	141
2014	120
2015	132
2016	124
2017	142
2018	134
2019	132
2020	107
2021	117
2022	134
2023	165
2024	121

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

See the data as a table

Year	Growing-season temperature
1937	16.1 °C
1938	15.8 °C
1939	16.1 °C
1940	16.3 °C
1941	15.0 °C
1942	14.6 °C
1943	15.0 °C
1944	15.0 °C
1945	14.1 °C
1946	15.3 °C
1947	15.2 °C
1948	14.9 °C
1949	16.3 °C
1950	13.4 °C
1951	13.0 °C
1952	15.7 °C
1953	14.3 °C
1954	13.7 °C
1955	14.1 °C
1956	14.9 °C
1957	15.4 °C
1958	15.4 °C
1959	14.4 °C
1960	15.3 °C
1961	15.3 °C
1962	14.6 °C
1963	15.5 °C
1964	14.8 °C
1965	13.7 °C
1966	15.1 °C
1967	15.1 °C
1968	13.6 °C
1969	16.2 °C
1970	15.2 °C
1971	15.6 °C
1972	14.6 °C
1973	15.6 °C
1974	15.0 °C
1975	13.2 °C
1976	15.9 °C
1977	14.7 °C
1978	14.7 °C
1979	15.2 °C
1980	15.6 °C
1981	15.0 °C
1982	13.0 °C
1983	14.2 °C
1984	14.6 °C
1985	14.8 °C
1986	14.4 °C
1987	15.9 °C
1988	16.0 °C
1989	14.2 °C
1990	14.9 °C
1991	14.6 °C
1992	14.3 °C
1993	12.5 °C
1994	15.2 °C
1995	12.8 °C
1996	13.8 °C
1997	13.6 °C
1998	15.2 °C
1999	12.9 °C
2000	14.8 °C
2001	15.4 °C
2002	13.4 °C
2003	15.4 °C
2004	13.4 °C
2005	14.1 °C
2006	15.8 °C
2007	15.5 °C
2008	13.8 °C
2009	14.2 °C
2010	13.2 °C
2011	14.2 °C
2012	15.8 °C
2013	15.0 °C
2014	14.4 °C
2015	15.0 °C
2016	14.5 °C
2017	15.3 °C
2018	14.3 °C
2019	14.0 °C
2020	14.2 °C
2021	15.1 °C
2022	14.9 °C
2023	15.3 °C
2024	15.0 °C

What this means for you: Since 1938, Great Falls's last spring frost has come about 1 day later per decade, on average. The frost-free season has shrunk 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 Great Falls Ap (NOAA GHCN-Daily). Years with too many missing days are left out.

Nearby towns

Malmstrom Air Force Base Sun Prairie Fort Benton Choteau Conrad Helena Valley Northeast