When to plant in Mercer, PA
Planting dates worked out from Mercer's own frost records, not a generic zone chart.
Safe to plant out
May 25
1 year in 10 has a later frost
Average last frost
May 10
about a 50% chance of a later one
Average first fall frost
Oct 10
1 year in 10 by Sep 29
Frost-free days
150
median, 1991–2020
Station used: Slippery Rock 1 Ssw · 24.3 km away · station 384 m, town 395 m. How we match towns to stations
This season
Plan your garden.
Planting dates for common crops
| Crop | Start indoors | Plant out or sow | Harvest from |
|---|---|---|---|
| Tomato | Mar 30 – Apr 13 | May 25 – Jun 8 | Jul 19 |
| Sweet pepper | Mar 16 – Mar 30 | May 25 – Jun 8 | Jul 24 |
| Lettuce (leaf) | Mar 8 – Mar 15 | Apr 12 – Apr 26 | May 22 |
| Peas | — | Apr 1 – Apr 29 | May 26 |
| Bush beans | — | May 18 – Jun 8 | Jul 7 |
| Carrot | — | Apr 19 – May 31 | Jun 18 |
| Beet | — | Apr 12 – May 24 | Jun 1 |
| Potato | — | Apr 19 – May 10 | Jun 28 |
| Kale | Mar 1 – Mar 15 | Apr 12 – Apr 26 | May 25 |
| Broccoli | Mar 1 – Mar 15 | Apr 12 – May 3 | Jun 11 |
| Cucumber | Apr 27 – May 4 | May 25 – Jun 8 | Jul 14 |
| Summer squash and zucchini | Apr 27 – May 4 | May 25 – Jun 8 | Jul 9 |
| Winter squash | Apr 27 – May 4 | May 25 – Jun 8 | Aug 13 |
| Sweet corn | — | May 18 – Jun 8 | Jul 17 |
| Onion (from sets) | — | Apr 12 – May 3 | Jul 11 |
| Garlic | — | Sep 26 – Oct 24 (fall) | following summer |
| Spinach | — | Apr 1 – Apr 29 | May 9 |
| Basil | Apr 13 – Apr 27 | May 25 – Jun 8 | Jul 21 |
Mercer'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 |
|---|---|
| 1950 | May 9 |
| 1951 | Apr 24 |
| 1952 | Apr 16 |
| 1953 | Apr 27 |
| 1954 | May 5 |
| 1955 | May 9 |
| 1956 | May 25 |
| 1957 | May 3 |
| 1958 | Apr 30 |
| 1959 | Apr 23 |
| 1960 | Apr 19 |
| 1961 | May 17 |
| 1962 | May 9 |
| 1963 | May 24 |
| 1964 | Apr 25 |
| 1965 | Apr 28 |
| 1966 | May 11 |
| 1969 | May 27 |
| 1970 | May 8 |
| 1971 | May 28 |
| 1972 | Jun 12 |
| 1973 | May 16 |
| 1974 | May 8 |
| 1975 | May 14 |
| 1976 | May 23 |
| 1977 | Jun 8 |
| 1978 | Jun 14 |
| 1979 | May 18 |
| 1980 | Jun 17 |
| 1981 | May 21 |
| 1982 | May 9 |
| 1983 | May 27 |
| 1984 | May 17 |
| 1985 | May 9 |
| 1986 | May 3 |
| 1987 | May 6 |
| 1988 | May 26 |
| 1989 | May 7 |
| 1990 | Jun 5 |
| 1991 | Apr 24 |
| 1992 | May 28 |
| 1993 | May 21 |
| 1994 | May 27 |
| 1995 | May 8 |
| 1996 | May 14 |
| 1997 | May 23 |
| 1998 | Jun 9 |
| 1999 | Apr 26 |
| 2000 | May 2 |
| 2001 | Apr 29 |
| 2002 | May 22 |
| 2003 | Apr 26 |
| 2004 | May 4 |
| 2005 | May 5 |
| 2006 | May 23 |
| 2007 | Apr 14 |
| 2008 | Apr 16 |
| 2009 | May 19 |
| 2010 | May 10 |
| 2011 | May 5 |
| 2012 | May 12 |
| 2013 | May 25 |
| 2014 | May 6 |
| 2016 | May 17 |
| 2017 | May 10 |
| 2018 | May 2 |
| 2019 | Apr 29 |
| 2020 | May 14 |
| 2021 | May 14 |
| 2022 | Apr 30 |
| 2023 | Apr 27 |
| 2024 | Apr 26 |
| 2025 | Apr 18 |
| 2026 | May 13 |
Each year's frost-free daysLong-term trend
See the data as a table
| Year | Frost-free days |
|---|---|
| 1951 | 168 |
| 1952 | 170 |
| 1953 | 163 |
| 1954 | 154 |
| 1955 | 168 |
| 1956 | 137 |
| 1957 | 146 |
| 1958 | 154 |
| 1959 | 146 |
| 1960 | 187 |
| 1961 | 173 |
| 1962 | 167 |
| 1963 | 141 |
| 1964 | 163 |
| 1965 | 159 |
| 1966 | 159 |
| 1969 | 124 |
| 1970 | 161 |
| 1971 | 132 |
| 1972 | 119 |
| 1973 | 158 |
| 1974 | 137 |
| 1975 | 122 |
| 1976 | 140 |
| 1977 | 127 |
| 1978 | 103 |
| 1979 | 113 |
| 1980 | 109 |
| 1981 | 130 |
| 1982 | 110 |
| 1983 | 117 |
| 1985 | 125 |
| 1986 | 126 |
| 1987 | 149 |
| 1988 | 129 |
| 1989 | 141 |
| 1990 | 135 |
| 1991 | 155 |
| 1992 | 124 |
| 1993 | 131 |
| 1994 | 127 |
| 1995 | 136 |
| 1996 | 141 |
| 1997 | 131 |
| 1998 | 134 |
| 1999 | 162 |
| 2000 | 148 |
| 2001 | 160 |
| 2002 | 143 |
| 2003 | 158 |
| 2004 | 153 |
| 2005 | 176 |
| 2006 | 143 |
| 2007 | 196 |
| 2008 | 184 |
| 2009 | 151 |
| 2010 | 161 |
| 2012 | 148 |
| 2013 | 151 |
| 2016 | 149 |
| 2017 | 143 |
| 2018 | 166 |
| 2019 | 168 |
| 2021 | 171 |
| 2023 | 178 |
| 2025 | 174 |
Each year's average temperature, April to SeptemberLong-term trend
See the data as a table
| Year | Growing-season temperature |
|---|---|
| 1950 | 15.5 °C |
| 1951 | 16.2 °C |
| 1952 | 17.3 °C |
| 1953 | 17.9 °C |
| 1954 | 17.7 °C |
| 1955 | 19.0 °C |
| 1956 | 16.5 °C |
| 1957 | 17.9 °C |
| 1958 | 17.0 °C |
| 1959 | 19.1 °C |
| 1960 | 18.0 °C |
| 1961 | 17.3 °C |
| 1962 | 17.6 °C |
| 1963 | 16.5 °C |
| 1964 | 17.8 °C |
| 1965 | 17.5 °C |
| 1966 | 16.8 °C |
| 1967 | 16.3 °C |
| 1968 | 16.7 °C |
| 1969 | 16.2 °C |
| 1970 | 17.0 °C |
| 1971 | 15.6 °C |
| 1972 | 15.9 °C |
| 1973 | 16.6 °C |
| 1974 | 14.8 °C |
| 1975 | 14.9 °C |
| 1976 | 15.0 °C |
| 1977 | 16.6 °C |
| 1978 | 15.5 °C |
| 1979 | 15.0 °C |
| 1980 | 15.8 °C |
| 1981 | 15.7 °C |
| 1982 | 15.0 °C |
| 1983 | 15.6 °C |
| 1985 | 15.7 °C |
| 1986 | 16.4 °C |
| 1987 | 16.6 °C |
| 1988 | 16.2 °C |
| 1989 | 15.5 °C |
| 1990 | 15.4 °C |
| 1991 | 17.4 °C |
| 1992 | 14.8 °C |
| 1993 | 15.8 °C |
| 1994 | 15.3 °C |
| 1995 | 16.5 °C |
| 1996 | 16.2 °C |
| 1997 | 15.3 °C |
| 1998 | 17.4 °C |
| 1999 | 17.5 °C |
| 2000 | 16.8 °C |
| 2001 | 17.2 °C |
| 2002 | 18.1 °C |
| 2003 | 17.0 °C |
| 2004 | 17.4 °C |
| 2005 | 18.1 °C |
| 2006 | 17.5 °C |
| 2007 | 17.6 °C |
| 2008 | 17.2 °C |
| 2009 | 16.9 °C |
| 2010 | 18.9 °C |
| 2011 | 18.4 °C |
| 2012 | 18.4 °C |
| 2013 | 17.7 °C |
| 2014 | 18.2 °C |
| 2016 | 17.5 °C |
| 2017 | 16.9 °C |
| 2018 | 17.4 °C |
| 2019 | 17.2 °C |
| 2020 | 16.3 °C |
| 2021 | 16.7 °C |
| 2022 | 16.6 °C |
| 2023 | 16.8 °C |
| 2025 | 17.4 °C |
| 2026 | 17.8 °C |
What this means for you: Since 1950, Mercer's last spring frost has stayed at about the same time of year. The frost-free season has grown by about 1 days per decade. Year-to-year swings are large, so keep using the safe date rather than the trend.
Source: daily records from Slippery Rock 1 Ssw (NOAA GHCN-Daily). Years with too many missing days are left out.