Frost dates for Mercer, PA
At Mercer, the median last spring frost (32°F) is May 15 and the median first fall frost is Oct 3, for a typical growing season of 140 days. For a 90% chance that the last frost has passed, wait until Jun 1. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 15Last spring frost (median)50% chance of 32°F after this date
- Jun 1Safer planting date10% chance of 32°F after this date
- Oct 3First fall frost (median)50% chance of 32°F by this date
- 140 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | May 10 | May 27 | Jun 19 |
| 32°F | Apr 30 | May 15 | Jun 1 |
| 28°F | Apr 19 | May 3 | May 21 |
| 24°F | Apr 8 | Apr 24 | May 10 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Sep 4 | Sep 23 | Oct 6 |
| 32°F | Sep 19 | Oct 3 | Oct 19 |
| 28°F | Sep 29 | Oct 13 | Nov 1 |
| 24°F | Oct 8 | Oct 29 | Nov 12 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 86 days | 118 days | 140 days |
| 32°F | 117 days | 140 days | 163 days |
| 28°F | 140 days | 163 days | 185 days |
| 24°F | 160 days | 186 days | 209 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 16137 | 6a | -10 to -5°F | 1 km |
| 16133 | 6a | -10 to -5°F | 11 km |
| 16124 | 6a | -10 to -5°F | 12 km |
| 16142 | 6a | -10 to -5°F | 13 km |
| 16156 | 6a | -10 to -5°F | 14 km |
| 16148 | 6a | -10 to -5°F | 15 km |
| 16153 | 6a | -10 to -5°F | 16 km |
| 16113 | 6a | -10 to -5°F | 17 km |
| 16150 | 6a | -10 to -5°F | 19 km |
| 16154 | 6a | -10 to -5°F | 19 km |
| 16114 | 6a | -10 to -5°F | 20 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00365651, at 41.2247, -80.2350, elevation 372 m (1,220 ft).
- Data quality: Representative (10+ years), 16 years of freeze data.
- Average days per year at or below 32°F: 158.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Slippery Rock 1 SSW (24 km)
- New Castle 1 N (25 km)
- Jamestown 2 NW (36 km)
- Franklin (39 km)
- Port Meadville Airport (45 km)
- Linesville 1 S (49 km)
- Butler 2 SW (50 km)
- Beaver Falls 1 NE (52 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.