Frost dates for 03230Danbury, NH
The average last spring frost in Danbury is May 21 and the average first fall frost is September 26, giving a typical growing season of about 127 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 21
- Average first fall frost
- Sep 26
- Growing season
- 127 days
Safer after Jun 5 (1-in-10 risk)
Possible by Sep 12 (1-in-10 risk)
Last frost typically in 199 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 20 · Jun 2 · Jun 17 | Aug 31 · Sep 14 · Sep 29 | 104 days | 100% |
| Frost / freeze (32°F) | May 7 · May 21 · Jun 5 | Sep 12 · Sep 26 · Oct 7 | 127 days | 100% |
| Hard freeze (28°F) | Apr 26 · May 8 · May 23 | Sep 23 · Oct 5 · Oct 18 | 150 days | 100% |
Planting calendar for Danbury
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 20 – Jun 26 |
| Tomatoes | Transplant outdoors | Jun 6 – Jun 6 |
| Peppers | Start seeds indoors | Apr 20 – May 21 |
| Peppers | Transplant outdoors | Jun 20 – Jul 21 |
| Eggplant | Start seeds indoors | May 7 – Jun 5 |
| Eggplant | Transplant outdoors | Jun 20 – Jul 21 |
| Cucumbers | Sow outdoors | Jun 20 – Jun 16 |
| Summer squash | Sow outdoors | Jun 6 – Jul 21 |
| Winter squash & pumpkins | Sow outdoors | Jun 20 – Jul 21 |
| Snap beans | Sow outdoors | Jun 6 – Jul 9 |
| Sweet corn | Sow outdoors | Jun 6 – Jun 6 |
| Watermelon & cantaloupe | Sow outdoors | Jun 20 – Jul 21 |
| Okra | Sow outdoors | Jun 13 – Jul 6 |
| Peas | Sow outdoors (spring) | Apr 20 – Jun 5 |
| Potatoes | Plant outdoors (spring) | Apr 20 – Jun 20 |
| Onions | Start seeds indoors (spring) | Mar 9 – Apr 5 |
| Onions | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (spring) | Apr 2 – May 6 |
| Broccoli | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (fall) | May 27 – Jun 6 |
| Broccoli | Transplant outdoors (fall) | Jun 26 – Jul 7 |
| Cabbage | Start seeds indoors (spring) | Mar 23 – Apr 20 |
| Cabbage | Transplant outdoors (spring) | Apr 20 – May 21 |
| Cabbage | Start seeds indoors (fall) | May 17 – Jun 16 |
| Cabbage | Transplant outdoors (fall) | Jun 16 – Jul 17 |
| Leaf lettuce | Sow outdoors (spring) | Apr 20 – Jul 6 |
| Leaf lettuce | Sow outdoors (fall) | Jun 16 – Aug 2 |
| Spinach | Sow outdoors (spring) | Apr 13 – May 27 |
| Spinach | Sow outdoors (fall) | Jul 3 – Aug 7 |
| Radishes | Sow outdoors (spring) | Apr 20 – Jun 10 |
| Radishes | Sow outdoors (fall) | Jun 16 – Aug 17 |
| Kale | Sow outdoors (spring) | May 7 – May 27 |
| Kale | Sow outdoors (fall) | Jun 9 – Jul 17 |
| Carrots | Sow outdoors (spring) | May 21 – Jul 6 |
| Carrots | Sow outdoors (fall) | May 17 – Jul 2 |
| Garlic | Plant outdoors (fall) | Sep 16 – Oct 17 |
Where these dates come from
ZIP code 03230 is matched to the NOAA station Grafton, NH, 9 km away, at 830 ft elevation (13 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Grafton, NH (used) | 830 ft | May 21 | Sep 26 |
| Franklin Falls Dam, NH | 450 ft | May 7 | Oct 3 |
| Salisbury, NH | 550 ft | May 14 | Sep 29 |
| Mt Sunapee, NH | 1,275 ft | May 2 | Oct 9 |
Frost dates near Danbury
- Wilmot, NH 03287 · last May 14, first Oct 1
- Grafton, NH 03240 · last May 21, first Sep 26
- East Andover, NH 03231 · last May 14, first Sep 29
- Hill, NH 03243 · last Apr 30, first Oct 18
- Elkins, NH 03233 · last May 14, first Oct 1
- Andover, NH 03216 · last May 14, first Sep 29
- New London, NH 03257 · last May 2, first Oct 9
- Springfield, NH 03284 · last May 2, first Oct 9
Frequently asked questions
- When is the last frost in Danbury, NH?
- For ZIP code 03230, the average last spring frost (32°F) is May 21, based on NOAA 1991-2020 climate normals for the Grafton, NH weather station. There is a 1-in-10 chance of a frost after June 5.
- When is the first frost in Danbury, NH?
- The average first fall frost (32°F) is September 26. There is a 1-in-10 chance of frost by September 12, so tender plants are at risk from that point on.
- How long is the growing season in 03230?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 127 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.