Frost dates in Boston: last spring frost and first autumn frost
When is it safe to plant out in Boston, and when does the first frost come? Dates from 45 years of nightly minimum temperatures (1981–2025), with how early or late they can fall.
Frost dates in Boston and how sure they are
| Early year (1 in 10) | Typical (median) | Late year (1 in 10) | |
|---|---|---|---|
| Last spring frost | 11 April | 22 April | 30 April |
| First autumn frost | 13 October | 29 October | 9 November |
In a typical year the last frost in Boston falls around 22 April and the first one around 29 October, leaving about 190 frost-free days (between 168 and 208 in 8 years out of 10). To be safe, plant tender crops after 30 April: by then the last frost has passed in 9 years out of 10. Bring them in before 13 October: in 1 year in 10 the first frost comes earlier.
Frost month by month in Boston
| Month | Average low | Coldest night (avg) | Record low | Frost nights | Years with frost |
|---|---|---|---|---|---|
| January | -7.7 °C | -17.6 °C | -25.1 °C | 28.4 | 100% |
| February | -6.8 °C | -16.3 °C | -25.7 °C | 25.5 | 100% |
| March | -2.9 °C | -12 °C | -19.2 °C | 23.5 | 100% |
| April | 2.4 °C | -3.3 °C | -10.3 °C | 7.6 | 98% |
| May | 8.2 °C | 2.2 °C | -0.9 °C | 0.1 | 9% |
| June | 13.5 °C | 7.8 °C | 4.8 °C | 0 | 0% |
| July | 17.1 °C | 12.7 °C | 7.4 °C | 0 | 0% |
| August | 16.5 °C | 11.4 °C | 6.6 °C | 0 | 0% |
| September | 12.5 °C | 6.2 °C | 1.6 °C | 0 | 0% |
| October | 6.7 °C | -0.2 °C | -5.6 °C | 1.4 | 60% |
| November | 1.2 °C | -5.6 °C | -12.2 °C | 12.7 | 100% |
| December | -3.8 °C | -12.6 °C | -20.1 °C | 25 | 100% |
Frost here means a night minimum at or below 0 °C at 2 m. Frost nights is the average count per month; years with frost is how many years had at least one.
Frost alerts for your garden or field
LayEarth Business Agro sends an alert when the forecast low at your saved site drops below your threshold (0 °C by default), with frost risk, hours below zero and white or black frost for each forecast day. LayEarth Pro, from 9 USD a month, adds alerts for the places you follow.
Temperature map around Boston
The live temperature layer of the map (NOAA GFS forecast): watch the cold nights coming hour by hour.
More for Boston
Weather in Boston now · Will it rain today in Boston? · Open the temperature map on Boston
Questions
- When is the last frost in Boston?
- On average around 22 April. In an early year the last frost comes by 11 April, in a late one (1 year in 10) after 30 April.
- When is the first frost in Boston?
- On average around 29 October. In 1 year in 10 it comes before 13 October, in a mild year not until 9 November.
- How long is the growing season in Boston?
- About 190 frost-free days between the last spring frost and the first autumn frost, from 168 in a short year to 208 in a long one.
- When can I plant tomatoes in Boston?
- Frost-tender plants such as tomatoes, peppers, beans and courgettes go out after the last frost: after 30 April the risk is down to 1 year in 10. Hardy crops can go earlier.
- How cold does it get in Boston?
- The coldest night of winter averages -19.1 °C; the lowest since 1981 was -25.7 °C in 2015.
Frost dates nearby
New York · Montreal · Philadelphia · Quebec City · Ottawa · Baltimore
How these dates are computed
Daily minimum temperature at 2 m from NASA POWER (MERRA-2 reanalysis, public domain), 1981–2025, corrected from the ~50 km grid to the real altitude of Boston (6.5 °C per km). For each year: the last night at or below 0 °C before midsummer and the first one after it; the dates are the median and the 10% / 90% of those years. A garden in a frost pocket or a city centre can differ by days. Live temperatures: the temperature layer of the map.