GreenlyFrost dates and when to plant in Connecticut
United States
In Connecticut the last spring frost comes between 6 April (New Haven) and 13 April (Hartford) — the median of 2016–2025 in 2 cities. The first autumn frost comes between 8 November (Hartford) and 12 November (New Haven). The frost-free season lasts 209–220 days. Tomato: plant out into open ground 17 May – 23 July, earliest in New Haven, latest in New Haven.
Frost dates by city in Connecticut
| City | Last spring frost | First autumn frost | Frost-free days | Climate zone | Tomato: window |
|---|---|---|---|---|---|
| New Haven | 6 April | 12 November | 220 | 210–269 frost-free days | 17 May – 23 July |
| Hartford | 13 April | 8 November | 209 | 150–209 frost-free days | 19 May – 19 July |
Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.
When to plant in Connecticut: windows by crop
The earliest start and the latest end among the cities here, each with its city; every city’s own window is on its page. Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.
| Crop | Planting out or sowing |
|---|---|
| Tomato | 17 May (New Haven) – 23 July (New Haven) |
| Cucumber | 26 May (New Haven) – 28 August (New Haven) |
| Bell Pepper, Eggplant | 26 May (New Haven) – 23 July (New Haven) |
| Zucchini | 26 May (New Haven) – 26 August (New Haven) |
| Pumpkin | 26 May (New Haven) – 18 July (New Haven) |
| Watermelon | 26 May (New Haven) – 3 August (New Haven) |
| Peas | 16 March (New Haven) – 30 August (New Haven) |
| Garlic, Tulip, Daffodil, Crocus, Hyacinth | Autumn planting: 9 October (Hartford) – end of December (New Haven) |
Weather by month in Connecticut
Across the 2 cities the warmest month is July (average days 28.2 … 29.5 °C) and the coldest January (average nights -5.1 … -3.4 °C). Every city averages below 0 °C at night in December–February.
| Month | Day, °C | Night, °C | Rain, mm |
|---|---|---|---|
| January | 3.4 … 4 °C | -5.1 … -3.4 °C | 103 |
| February | 5.4 … 5.7 °C | -4.5 … -2.8 °C | 94 |
| March | 9.3 … 9.6 °C | -1 … 0.3 °C | 112 |
| April | 14.2 … 15 °C | 4.1 … 5.1 °C | 127 |
| May | 19.4 … 20.8 °C | 9.9 … 10.5 °C | 116 |
| June | 24.9 … 26.5 °C | 15.2 … 15.9 °C | 82 |
| July | 28.2 … 29.5 °C | 19 … 20.1 °C | 131 |
| August | 27.1 … 28.1 °C | 18.1 … 19.2 °C | 99 |
| September | 23.6 … 24.1 °C | 14.5 … 15.8 °C | 123 |
| October | 18.1 … 18.2 °C | 8.9 … 10.4 °C | 126 |
| November | 10.8 … 11.5 °C | 1.9 … 3.5 °C | 85 |
| December | 5.2 … 6 °C | -2.9 … -1.1 °C | 127 |
Day and night: the lowest … highest monthly average among the cities; rain: the middle city (ERA5 via Open-Meteo).
What to plant month by month: the Northeast and Midwest
Other regions: United States
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York State
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington State
- West Virginia
- Wisconsin
More about the United States
- Gardening in the United States: climate zones and crops by region
- United States: frost dates by city
- When to plant tomatoes in the United States
- When to plant cucumbers in the United States
- When to plant bell peppers in the United States
- When to plant peas in the United States
- When to plant garlic in the United States
- Gardening by country
