GreenlyBoston: frost dates
United States
In Boston the last spring frost usually comes around 9 April and the first autumn frost around 13 November, which leaves about 218 frost-free days (median of 2016–2025). Tomato seedlings can go into open ground around 19 May.
| Last spring frost | around 9 April |
|---|---|
| First autumn frost | around 13 November |
| Frost-free days | 218 days |
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 sow and plant
| Crop | Sow for seedlings | Plant out in a greenhouse | Open ground |
|---|---|---|---|
| Bell Pepper | 23 February | 8 May | 29 May |
| Chili Pepper | 7 March | 20 May | 10 June |
| Corn | — | 15 April | sow 6 May |
| Cucumber | 27 March | 8 May | 29 May |
| Eggplant | 27 February | 8 May | 29 May |
| Green Beans | 9 March | 15 April | 6 May |
| Melon | 17 March | 8 May | 29 May |
| Peas | — | 26 February | sow 19 March |
| Physalis | 14 March | 28 April | 19 May |
| Pumpkin | 22 March | 28 April | 19 May |
| Sweet Corn | — | 15 April | sow 6 May |
| Tomato | 2 March | 28 April | 19 May |
| Watermelon | 6 April | 8 May | 29 May |
| Zucchini | 27 March | 28 April | 19 May |
Planting out: a week after the last frost once the soil is warm enough for the crop; frost-hardy crops three weeks before it; an unheated greenhouse three weeks earlier. Seedlings are sown so they are ready on that day.
Boston: weather for the next 7 days
Forecast by Open-Meteo. Nights at or below 0 °C are marked as frost.
Planted in autumn
| Crop | Plant around |
|---|---|
| Crocus | 14 October |
| Daffodil | 14 October |
| Garlic | 14 October |
| Hyacinth | 14 October |
| Lily | 14 October |
| Tulip | 14 October |
A month before the first autumn frost, so the roots grow before winter.