Frost dates for Grafton, NH
At Grafton, the median last spring frost (32°F) is May 21 and the median first fall frost is Sep 26, for a typical growing season of 127 days. For a 90% chance that the last frost has passed, wait until Jun 5. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 21Last spring frost (median)50% chance of 32°F after this date
- Jun 5Safer planting date10% chance of 32°F after this date
- Sep 26First fall frost (median)50% chance of 32°F by this date
- 127 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 20 | Jun 2 | Jun 17 |
| 32°F | May 7 | May 21 | Jun 5 |
| 28°F | Apr 26 | May 8 | May 23 |
| 24°F | Apr 12 | Apr 25 | May 7 |
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 | Aug 31 | Sep 14 | Sep 29 |
| 32°F | Sep 12 | Sep 26 | Oct 7 |
| 28°F | Sep 23 | Oct 5 | Oct 18 |
| 24°F | Oct 2 | Oct 15 | Nov 2 |
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 | 83 days | 104 days | 124 days |
| 32°F | 107 days | 127 days | 145 days |
| 28°F | 130 days | 150 days | 168 days |
| 24°F | 155 days | 174 days | 194 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 |
|---|---|---|---|
| 03240 | 5a | -20 to -15°F | 1 km |
| 03230 | 5a | -20 to -15°F | 8 km |
| 03284 | 5b | -15 to -10°F | 12 km |
| 03741 | 5a | -20 to -15°F | 13 km |
| 03287 | 5b | -15 to -10°F | 14 km |
| 03748 | 5a | -20 to -15°F | 14 km |
| 03222 | 5b | -15 to -10°F | 15 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 USC00273530, at 43.5667, -71.9500, elevation 253 m (830 ft).
- Data quality: Representative (10+ years), 12 years of freeze data.
- Average days per year at or below 32°F: 199.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Franklin Falls Dam (26 km)
- Mount Sunapee (28 km)
- Newport (28 km)
- Salisbury (29 km)
- Lebanon Muni Airport (29 km)
- Hanover (31 km)
- Wentworth (33 km)
- Plymouth (34 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.