Thornton, NH frost dates
Last spring frostMay 15median date
First fall frostSep 28median date
Growing season136 daysfrost-free
Hardiness zone5aZone 5a
How Thornton compares
- In 8 years out of 10, the last spring frost in Thornton falls between May 3 and May 29, a 26-day window. The first fall frost falls between September 13 and October 11.
- The median last frost is 8 days later than the New Hampshire median of May 7.
- Its 136-day growing season is longer than 17% of the 252 New Hampshire places with a regular frost season (state median 150 days).
- The last frost is 12 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 188 nights a year at or below 32°F.
- Compared with Manchester, NH, 103 km away, the last frost here is 15 days later than there and the growing season is 28 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 3 |
| 50% (median) | May 15 |
| 10% (safe for tender plants) | May 29 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 13 |
| 50% (median) | September 28 |
| 90% (late) | October 11 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Thornton, NH
Thornton, NH frost dates — last frost May 15, first frost Sep 28, zone 5a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 17 to May 1
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 20 to Apr 3Transplant outside: May 22 to Jun 5
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Sow outdoors: Apr 17 to May 22Plant for fall: Aug 3 to Aug 31
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 17 to May 1Sow outdoors: Apr 17 to May 1Plant for fall: Jul 20 to Aug 10
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 22 to Jul 13
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Plant for fall: Jun 22 to Jul 13
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 22 to Jul 13
Start indoors: Apr 3 to Apr 17Transplant outside: Jun 5 to Jun 19Sow outdoors: Jun 5 to Jun 19
Start indoors: Apr 3 to Apr 17Transplant outside: May 22 to Jun 5
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 6 to Jul 27
Sow outdoors: Apr 3 to Apr 24Plant for fall: Aug 3 to Aug 24
Sow outdoors: Apr 10 to May 22Plant for fall: Aug 17 to Sep 7
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 5Sow outdoors: May 22 to Jun 5Plant for fall: Jul 13 to Jul 27
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5Plant for fall: Jul 20 to Aug 3
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 12
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 6 to Jul 20
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 20 to Aug 3
Sow outdoors: Apr 24 to May 15
Sow outdoors: May 1 to May 29Plant for fall: Jul 20 to Aug 3
Sow outdoors: May 1 to May 22Plant for fall: Aug 3 to Aug 24
Sow outdoors: May 22 to Jun 12Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 22 to Jun 5
Transplant outside: May 29 to Jun 19
Plant for fall: Sep 14 to Oct 19
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Thornton, NH
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 20 – Mar 6 | Apr 17 – May 1 | — | — |
| Peppers | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Eggplant | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Tomatoes | Mar 20 – Apr 3 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 20 – Apr 3 | Apr 24 – May 8 | Apr 17 – May 22 | Aug 3 – Aug 31 |
| Kale | Mar 20 – Apr 3 | Apr 17 – May 1 | Apr 17 – May 1 | Jul 20 – Aug 10 |
| Broccoli | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 22 – Jul 13 |
| Cabbage | Mar 20 – Apr 3 | Apr 24 – May 8 | — | Jun 22 – Jul 13 |
| Cauliflower | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 22 – Jul 13 |
| Okra | Apr 3 – Apr 17 | Jun 5 – Jun 19 | Jun 5 – Jun 19 | — |
| Basil | Apr 3 – Apr 17 | May 22 – Jun 5 | — | — |
| Peas | — | — | Apr 3 – Apr 24 | Jul 6 – Jul 27 |
| Spinach | — | — | Apr 3 – Apr 24 | Aug 3 – Aug 24 |
| Radishes | — | — | Apr 10 – May 22 | Aug 17 – Sep 7 |
| Cucumbers | Apr 17 – Apr 24 | May 29 – Jun 5 | May 22 – Jun 5 | Jul 13 – Jul 27 |
| Zucchini & Summer Squash | Apr 17 – Apr 24 | — | May 22 – Jun 5 | Jul 20 – Aug 3 |
| Winter Squash & Pumpkins | Apr 17 – Apr 24 | — | May 22 – Jun 5 | — |
| Melons & Watermelon | Apr 17 – Apr 24 | May 29 – Jun 12 | — | — |
| Carrots | — | — | Apr 24 – May 22 | Jul 6 – Jul 20 |
| Beets | — | — | Apr 24 – May 22 | Jul 20 – Aug 3 |
| Potatoes | — | — | Apr 24 – May 15 | — |
| Swiss Chard | — | — | May 1 – May 29 | Jul 20 – Aug 3 |
| Cilantro | — | — | May 1 – May 22 | Aug 3 – Aug 24 |
| Green Beans | — | — | May 22 – Jun 12 | Jul 13 – Jul 27 |
| Sweet Corn | — | — | May 22 – Jun 5 | — |
| Sweet Potatoes | — | May 29 – Jun 19 | — | — |
| Garlic | — | — | — | Sep 14 – Oct 19 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Waterville Valley Nepp, NH weather station, 12 km away (elevation 1,430 ft (436 m)).
Frost dates near Thornton
- Campton May 20 · Sep 27
- Woodstock May 7 · Oct 4
- Waterville Valley May 15 · Sep 28
- North Woodstock May 7 · Oct 4
- Plymouth May 20 · Sep 27
- Lincoln May 7 · Oct 4
- Center Sandwich May 6 · Oct 6
- Holderness May 20 · Sep 27
- Rumney May 12 · Oct 6
- Warren May 12 · Oct 6
Frequently asked questions
When is the last frost in Thornton, NH?
The median last spring frost in Thornton, NH is May 15. There is still about a 10% chance of frost after May 29, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Thornton, NH?
The median first fall frost is September 28, with about a 10% chance of frost before September 13.
How long is the growing season in Thornton, NH?
About 136 days between the median last spring frost and first fall frost.
What planting zone is Thornton, NH?
Thornton, NH is in USDA hardiness zone 5a.