When to plant in Helena Valley Southeast, MT

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

Safe to plant out

May 29

1 year in 10 has a later frost

Average last frost

May 13

about a 50% chance of a later one

Average first fall frost

Sep 27

1 year in 10 by Sep 14

Frost-free days

142

median, 1991–2020

Station used: Helena Ap Asos · 5.3 km away · station 1178 m, town 1158 m. How we match towns to stations

This season

Plan your garden.

Build my Helena Valley Southeast plan

Planting dates for common crops

Crop	Start indoors	Plant out or sow	Harvest from
Tomato	Apr 3 – Apr 17	May 29 – Jun 12	Jul 23
Sweet pepper	Mar 20 – Apr 3	May 29 – Jun 12	Jul 28
Lettuce (leaf)	Mar 11 – Mar 18	Apr 15 – Apr 29	May 25
Peas	—	Apr 9 – May 7	Jun 3
Bush beans	—	May 22 – Jun 12	Jul 11
Carrot	—	Apr 23 – Jun 4	Jun 22
Beet	—	Apr 23 – Jun 4	Jun 12
Potato	—	Apr 23 – May 14	Jul 2
Kale	Mar 5 – Mar 19	Apr 16 – Apr 30	May 29
Broccoli	Mar 4 – Mar 18	Apr 15 – May 6	Jun 14
Cucumber	May 1 – May 8	May 29 – Jun 12	Jul 18
Summer squash and zucchini	May 1 – May 8	May 29 – Jun 12	Jul 13
Winter squash	May 1 – May 8	May 29 – Jun 12	Aug 17
Sweet corn	—	May 22 – Jun 12	Jul 21
Onion (from sets)	—	Apr 15 – May 6	Jul 14
Garlic	—	Sep 13 – Oct 11 (fall)	following summer
Spinach	—	Apr 9 – May 7	May 17
Basil	Apr 17 – May 1	May 29 – Jun 12	Jul 25

Plan all 65 crops for Helena Valley Southeast

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

Each year's frost-free daysLong-term trend

See the data as a table

Year	Frost-free days
1939	138
1940	151
1941	129
1942	110
1943	111
1944	116
1945	113
1946	125
1947	111
1948	141
1949	109
1950	100
1951	103
1952	126
1953	120
1954	122
1955	113
1956	116
1957	148
1958	125
1959	101
1960	121
1961	127
1962	134
1963	157
1964	109
1965	119
1966	133
1967	155
1968	138
1969	93
1970	118
1971	116
1972	119
1973	109
1974	119
1975	115
1976	115
1977	115
1978	131
1979	116
1980	133
1981	140
1982	106
1983	126
1984	137
1985	128
1986	127
1987	127
1988	115
1989	99
1990	148
1991	135
1992	100
1993	142
1994	144
1995	101
1996	107
1997	123
1998	108
1999	93
2000	143
2001	135
2002	130
2003	120
2004	138
2005	144
2006	156
2007	160
2008	150
2009	133
2010	143
2011	159
2012	128
2013	147
2015	147
2016	151
2017	138
2018	159
2019	147
2020	164
2021	130
2022	160
2023	178
2024	133

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

See the data as a table

Year	Growing-season temperature
1938	14.8 °C
1939	15.0 °C
1940	16.0 °C
1941	14.4 °C
1942	13.8 °C
1943	14.1 °C
1944	13.5 °C
1945	13.4 °C
1946	14.4 °C
1947	14.2 °C
1948	14.0 °C
1949	14.8 °C
1950	12.7 °C
1951	12.7 °C
1952	14.7 °C
1953	13.9 °C
1954	13.5 °C
1955	13.3 °C
1956	14.4 °C
1957	14.6 °C
1958	14.7 °C
1959	13.6 °C
1960	14.2 °C
1961	15.0 °C
1962	14.2 °C
1963	15.0 °C
1964	13.7 °C
1965	13.1 °C
1966	15.5 °C
1967	15.0 °C
1968	13.2 °C
1969	15.2 °C
1970	13.5 °C
1971	13.0 °C
1972	12.9 °C
1973	14.1 °C
1974	14.2 °C
1975	12.2 °C
1976	14.1 °C
1977	14.4 °C
1978	15.1 °C
1979	15.2 °C
1980	14.8 °C
1981	15.0 °C
1982	14.3 °C
1983	14.2 °C
1984	14.5 °C
1985	15.0 °C
1986	14.3 °C
1987	15.5 °C
1988	16.2 °C
1989	14.7 °C
1990	15.5 °C
1991	15.4 °C
1992	15.2 °C
1993	13.3 °C
1994	16.1 °C
1995	13.4 °C
1996	14.1 °C
1997	13.9 °C
1998	15.0 °C
1999	13.4 °C
2000	15.8 °C
2001	17.3 °C
2002	15.1 °C
2003	16.7 °C
2004	15.0 °C
2005	15.2 °C
2006	16.8 °C
2007	16.9 °C
2008	15.1 °C
2009	15.6 °C
2010	13.8 °C
2011	14.7 °C
2012	16.3 °C
2013	15.8 °C
2015	16.5 °C
2016	16.2 °C
2017	16.7 °C
2018	15.4 °C
2019	15.5 °C
2020	15.8 °C
2021	16.9 °C
2022	16.3 °C
2023	17.0 °C
2024	16.8 °C

What this means for you: Since 1939, Helena Valley Southeast'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 Helena Ap Asos (NOAA GHCN-Daily). Years with too many missing days are left out.

Nearby towns

East Helena Montana City Helena Helena Valley Northeast Helena Valley West Central Helena West Side