Frost dates for 06376South Lyme, CT
The average last spring frost in South Lyme is April 16 and the average first fall frost is October 28, giving a typical growing season of about 194 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 16
- Average first fall frost
- Oct 28
- Growing season
- 194 days
Safer after Apr 30 (1-in-10 risk)
Possible by Oct 13 (1-in-10 risk)
Last frost typically in 166 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) | Apr 18 · Apr 29 · May 11 | Oct 5 · Oct 16 · Oct 31 | 170 days | 100% |
| Frost / freeze (32°F) | Apr 3 · Apr 16 · Apr 30 | Oct 13 · Oct 28 · Nov 12 | 194 days | 100% |
| Hard freeze (28°F) | Mar 19 · Apr 3 · Apr 17 | Oct 25 · Nov 9 · Nov 27 | 220 days | 100% |
Planting calendar for South Lyme
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 | Mar 16 – May 22 |
| Tomatoes | Transplant outdoors | May 2 – Jul 8 |
| Peppers | Start seeds indoors | Mar 16 – Apr 16 |
| Peppers | Transplant outdoors | May 16 – Jun 16 |
| Eggplant | Start seeds indoors | Apr 2 – May 1 |
| Eggplant | Transplant outdoors | May 16 – Jun 16 |
| Cucumbers | Sow outdoors | May 16 – Jul 18 |
| Summer squash | Sow outdoors | May 2 – Jun 16 |
| Winter squash & pumpkins | Sow outdoors | May 16 – Jun 16 |
| Snap beans | Sow outdoors | May 2 – Aug 10 |
| Sweet corn | Sow outdoors | May 2 – Jul 8 |
| Watermelon & cantaloupe | Sow outdoors | May 16 – Jun 16 |
| Okra | Sow outdoors | May 9 – Jun 1 |
| Peas | Sow outdoors (spring) | Mar 16 – May 1 |
| Potatoes | Plant outdoors (spring) | Mar 16 – May 16 |
| Onions | Start seeds indoors (spring) | Feb 2 – Mar 1 |
| Onions | Transplant outdoors (spring) | Apr 2 – May 1 |
| Broccoli | Start seeds indoors (spring) | Feb 26 – Apr 1 |
| Broccoli | Transplant outdoors (spring) | Apr 2 – May 1 |
| Broccoli | Start seeds indoors (fall) | Jun 28 – Jul 8 |
| Broccoli | Transplant outdoors (fall) | Jul 28 – Aug 8 |
| Cabbage | Start seeds indoors (spring) | Feb 16 – Mar 16 |
| Cabbage | Transplant outdoors (spring) | Mar 16 – Apr 16 |
| Cabbage | Start seeds indoors (fall) | Jun 18 – Jul 18 |
| Cabbage | Transplant outdoors (fall) | Jul 18 – Aug 18 |
| Leaf lettuce | Sow outdoors (spring) | Mar 16 – Jun 1 |
| Leaf lettuce | Sow outdoors (fall) | Jul 18 – Sep 3 |
| Spinach | Sow outdoors (spring) | Mar 9 – Apr 22 |
| Spinach | Sow outdoors (fall) | Aug 4 – Sep 8 |
| Radishes | Sow outdoors (spring) | Mar 16 – May 6 |
| Radishes | Sow outdoors (fall) | Jul 18 – Sep 18 |
| Kale | Sow outdoors (spring) | Apr 2 – Apr 22 |
| Kale | Sow outdoors (fall) | Jul 11 – Aug 18 |
| Carrots | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Carrots | Sow outdoors (fall) | Jun 18 – Aug 3 |
| Garlic | Plant outdoors (fall) | Oct 18 – Nov 18 |
Where these dates come from
ZIP code 06376 is matched to the NOAA station Groton New London Ap, CT, 18.2 km away, at 10 ft elevation (30 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Groton New London Ap, CT (used) | 10 ft | Apr 16 | Oct 28 |
| Orient Pt Sp, NY | 3 ft | Apr 6 | Nov 17 |
| Groton, CT | 40 ft | Apr 8 | Nov 2 |
| Norwich Public Utility Plt, CT | 20 ft | Apr 14 | Oct 24 |
Frost dates near South Lyme
- Niantic, CT 06357 · last Apr 8, first Nov 2
- Old Lyme, CT 06371 · last Apr 8, first Nov 2
- East Lyme, CT 06333 · last Apr 8, first Nov 2
- Old Saybrook, CT 06475 · last Apr 16, first Oct 28
- Waterford, CT 06385 · last Apr 16, first Oct 28
- Essex, CT 06426 · last Apr 8, first Nov 2
- Centerbrook, CT 06409 · last Apr 8, first Nov 2
- New London, CT 06320 · last Apr 8, first Nov 2
Frequently asked questions
- When is the last frost in South Lyme, CT?
- For ZIP code 06376, the average last spring frost (32°F) is April 16, based on NOAA 1991-2020 climate normals for the Groton New London Ap, CT weather station. There is a 1-in-10 chance of a frost after April 30.
- When is the first frost in South Lyme, CT?
- The average first fall frost (32°F) is October 28. There is a 1-in-10 chance of frost by October 13, so tender plants are at risk from that point on.
- How long is the growing season in 06376?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 194 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.