Somerville, Massachusetts: planting zone & frost dates
Somerville is in USDA plant hardiness zone 7a, where the average coldest winter night reaches 0 to 5°F (-17.8 to -15.0°C). The typical last spring frost is around Apr 8 and the first fall frost around Nov 3.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 17 | Oct 29 |
| Typical planning date (30% risk) | Apr 8 | Nov 3 |
| Median (50%) | Apr 4 | Nov 9 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station BOSTON LOGAN INTL AP, MA (USW00014739), 5.0 mi (8.1 km) from the city center and 49 ft lower than the city center (-15 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Somerville
Somerville spans more than one half-zone. Share of the city's land area by zone (via its 4 ZIP codes): 7a (71%), 6b (29%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Somerville
Dates are counted from the 30%-risk frost dates above (last frost Apr 8, first frost Nov 3). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Feb 11 – Feb 25 | Apr 15 – Apr 29 | — | — |
| Pepper | Jan 28 – Feb 11 | Apr 22 – May 6 | — | — |
| Lettuce | Feb 25 – Mar 11 | Mar 25 – Apr 15 | Mar 11 – Apr 22 | Aug 25 – Sep 22 |
| Green Beans | — | — | Apr 15 – May 20 | Aug 11 – Aug 25 |
| Sweet Corn | — | — | Apr 15 – May 13 | — |
| Zucchini & Summer Squash | Mar 11 – Mar 18 | Apr 15 – Apr 29 | Apr 15 – May 6 | Aug 11 – Aug 25 |
| Cucumber | Mar 11 – Mar 18 | Apr 22 – Apr 29 | Apr 15 – May 6 | Aug 11 – Aug 25 |
| Carrot | — | — | Mar 18 – Apr 22 | Aug 11 – Aug 25 |
| Onion | Jan 14 – Jan 28 | Mar 11 – Mar 25 | — | — |
| Potato | — | Mar 11 – Apr 1 | — | — |
| Basil | Feb 25 – Mar 11 | Apr 22 – May 6 | Apr 22 – May 13 | — |
| Spinach | — | — | Feb 25 – Mar 25 | Sep 8 – Oct 6 |
| Kale | Feb 11 – Feb 25 | Mar 11 – Apr 1 | Mar 11 – Apr 1 | Aug 25 – Sep 22 |
| Broccoli | Feb 11 – Feb 25 | Mar 25 – Apr 15 | — | Aug 11 – Aug 25 |
| Peas | — | — | Feb 25 – Mar 18 | Aug 25 – Sep 8 |
| Eggplant | Jan 28 – Feb 11 | Apr 22 – May 6 | — | — |
| Cabbage | Feb 11 – Feb 25 | Mar 11 – Mar 25 | — | Aug 11 – Aug 25 |
| Radish | — | — | Mar 4 – Apr 22 | Sep 22 – Oct 20 |
| Strawberry | — | Mar 11 – Apr 1 | — | — |
| Beets | — | — | Mar 18 – Apr 29 | Aug 25 – Sep 8 |
Nearby cities in Massachusetts
- Cambridge — zone 6b, last frost Apr 8, first frost Nov 3
- Boston — zone 6b, last frost Apr 8, first frost Nov 3
- Newton — zone 6b, last frost Apr 24, first frost Oct 16
- Quincy — zone 6b, last frost Apr 30, first frost Oct 15
- Lynn — zone 7a, last frost May 1, first frost Oct 14
- Lawrence — zone 6b, last frost Apr 19, first frost Oct 22
More: all Massachusetts cities · other zone 7a cities: Louisville, KY, Wichita, KS, Cleveland, OH, Lexington, KY, St. Louis, MO, Boise, ID, Amarillo, TX, Providence, RI
Somerville gardening questions
When is the last frost in Somerville, MA?
Plan around Apr 8. At NOAA's Boston Logan Int'l Airport, MA station, 5.0 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 4, and after Apr 17 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Mar 28. The last frost is fairly predictable here: only 23 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Somerville, MA?
Start seeds indoors Feb 11 – Feb 25 and set transplants outside Apr 15 – Apr 29, once nights stay above 50°F and the soil is near 60°F. That leaves 209 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Somerville?
About 218 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 201 days, and in 1 year in 10 it runs 235 days or more. In fall there is a 10% chance of frost by Oct 29 and a 30% chance by Nov 3. That ranks 3rd longest of 13 Massachusetts cities on this site.
When should I plant a fall garden in Somerville?
Count back from the first fall frost (Nov 3): transplant broccoli Aug 11 – Aug 25; sow kale Aug 25 – Sep 22; sow lettuce Aug 25 – Sep 22; sow radishes Sep 22 – Oct 20. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 21. How the math works: succession and fall planting.
Did Somerville's hardiness zone change on the 2023 map?
Yes. Most of Somerville was zone 6b on the 2012 map and is zone 7a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Somerville in zone 7a?
No. Zone 7a covers about 71% of the city's land; the rest is in 6b (29%), measured across the city's 4 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.