Frost dates for 03242Henniker, NH
The average last spring frost in Henniker is May 6 and the average first fall frost is October 1, giving a typical growing season of about 146 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 6
- Average first fall frost
- Oct 1
- Growing season
- 146 days
Safer after May 20 (1-in-10 risk)
Possible by Sep 20 (1-in-10 risk)
Last frost typically in 186 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 6 · May 20 · Jun 3 | Sep 10 · Sep 23 · Oct 4 | 125 days | 100% |
| Frost / freeze (32°F) | Apr 27 · May 6 · May 20 | Sep 20 · Oct 1 · Oct 13 | 146 days | 100% |
| Hard freeze (28°F) | Apr 17 · Apr 27 · May 8 | Sep 30 · Oct 11 · Oct 28 | 166 days | 100% |
Planting calendar for Henniker
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 5 – Jun 11 |
| Tomatoes | Transplant outdoors | May 22 – Jun 11 |
| Peppers | Start seeds indoors | Apr 5 – May 6 |
| Peppers | Transplant outdoors | Jun 5 – Jul 6 |
| Eggplant | Start seeds indoors | Apr 22 – May 21 |
| Eggplant | Transplant outdoors | Jun 5 – Jul 6 |
| Cucumbers | Sow outdoors | Jun 5 – Jun 21 |
| Summer squash | Sow outdoors | May 22 – Jul 6 |
| Winter squash & pumpkins | Sow outdoors | Jun 5 – Jul 6 |
| Snap beans | Sow outdoors | May 22 – Jul 14 |
| Sweet corn | Sow outdoors | May 22 – Jun 11 |
| Watermelon & cantaloupe | Sow outdoors | Jun 5 – Jul 6 |
| Okra | Sow outdoors | May 29 – Jun 21 |
| Peas | Sow outdoors (spring) | Apr 5 – May 21 |
| Potatoes | Plant outdoors (spring) | Apr 5 – Jun 5 |
| Onions | Start seeds indoors (spring) | Feb 22 – Mar 21 |
| Onions | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (spring) | Mar 18 – Apr 21 |
| Broccoli | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (fall) | Jun 1 – Jun 11 |
| Broccoli | Transplant outdoors (fall) | Jul 1 – Jul 12 |
| Cabbage | Start seeds indoors (spring) | Mar 8 – Apr 5 |
| Cabbage | Transplant outdoors (spring) | Apr 5 – May 6 |
| Cabbage | Start seeds indoors (fall) | May 22 – Jun 21 |
| Cabbage | Transplant outdoors (fall) | Jun 21 – Jul 22 |
| Leaf lettuce | Sow outdoors (spring) | Apr 5 – Jun 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 21 – Aug 7 |
| Spinach | Sow outdoors (spring) | Mar 29 – May 12 |
| Spinach | Sow outdoors (fall) | Jul 8 – Aug 12 |
| Radishes | Sow outdoors (spring) | Apr 5 – May 26 |
| Radishes | Sow outdoors (fall) | Jun 21 – Aug 22 |
| Kale | Sow outdoors (spring) | Apr 22 – May 12 |
| Kale | Sow outdoors (fall) | Jun 14 – Jul 22 |
| Carrots | Sow outdoors (spring) | May 6 – Jun 21 |
| Carrots | Sow outdoors (fall) | May 22 – Jul 7 |
| Garlic | Plant outdoors (fall) | Sep 21 – Oct 22 |
Where these dates come from
ZIP code 03242 is matched to the NOAA station Hopkinton Lake, NH, 5.8 km away, at 430 ft elevation (19 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Hopkinton Lake, NH (used) | 430 ft | May 6 | Oct 1 |
| Weare 2 Ne, NH | 805 ft | May 9 | Oct 5 |
| Weare, NH | 720 ft | May 2 | Oct 8 |
| Bradford 2, NH | 815 ft | May 15 | Sep 27 |
Frost dates near Henniker
- Contoocook, NH 03229 · last May 6, first Oct 1
- Hillsborough, NH 03244 · last May 2, first Oct 8
- Warner, NH 03278 · last May 14, first Sep 29
- Bradford, NH 03221 · last May 15, first Sep 27
- Weare, NH 03281 · last May 2, first Oct 8
- Antrim, NH 03440 · last May 2, first Oct 8
- South Sutton, NH 03273 · last May 15, first Sep 27
- Concord, NH 03303 · last May 8, first Oct 3
Frequently asked questions
- When is the last frost in Henniker, NH?
- For ZIP code 03242, the average last spring frost (32°F) is May 6, based on NOAA 1991-2020 climate normals for the Hopkinton Lake, NH weather station. There is a 1-in-10 chance of a frost after May 20.
- When is the first frost in Henniker, NH?
- The average first fall frost (32°F) is October 1. There is a 1-in-10 chance of frost by September 20, so tender plants are at risk from that point on.
- How long is the growing season in 03242?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 146 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.