Portsmouth, RI planting zone & frost dates
Portsmouth is in USDA hardiness zone 7a. The last spring frost usually comes around April 11 and the first fall frost around November 2, for a growing season of about 203 days.
Planting calendar for Portsmouth
Dates are counted from the average last spring frost (April 11) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Feb 14 – Feb 28 Transplant outdoors: Apr 18 – Apr 25 |
| Peppers | Start seeds indoors: Jan 31 – Feb 14 Transplant outdoors: Apr 25 – May 2 |
| Eggplant | Start seeds indoors: Jan 31 – Feb 14 Transplant outdoors: Apr 25 – May 2 |
| Broccoli | Start seeds indoors: Jan 31 – Feb 14 Transplant outdoors: Mar 14 – Mar 28 |
| Cabbage | Start seeds indoors: Jan 31 – Feb 14 Transplant outdoors: Mar 14 – Mar 28 |
| Onions (sets) | Plant outdoors: Mar 14 – Mar 28 |
| Peas | Sow outdoors: Feb 28 – Mar 14 |
| Spinach | Sow outdoors: Feb 28 – Mar 14 |
| Lettuce | Sow outdoors: Mar 14 – Mar 28 |
| Carrots | Sow outdoors: Mar 14 – Mar 28 |
| Potatoes | Plant outdoors: Mar 14 – Mar 28 |
| Beans | Sow outdoors: Apr 18 – Apr 25 |
| Sweet corn | Sow outdoors: Apr 18 – Apr 25 |
| Cucumbers | Sow outdoors: Apr 18 – Apr 25 |
| Squash & zucchini | Sow outdoors: Apr 18 – Apr 25 |
| Basil | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: Apr 18 – Apr 25 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 7 (8 weeks before the average first fall frost on Nov 2).
Useful for zone 7a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 1 | Apr 11 | Apr 22 |
| First 32°F frost in fall is before | Nov 15 | Nov 2 | Oct 20 |
How to read it: in spring there is a 10% chance of a frost after April 22, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 20. A hard freeze (28°F) usually ends around March 31.
Hardiness zone by ZIP code in Portsmouth
- 02871 zone 7a
Nearby cities
- Middletown zone 7a, last frost Apr 11
- Bristol zone 7a, last frost Apr 11
- Newport East zone 7a, last frost Apr 11
- Newport zone 7a, last frost Apr 7
- Warren zone 7a, last frost Apr 11
- Barrington zone 7a, last frost Apr 11
- Warwick zone 7a, last frost Apr 11
- East Greenwich zone 7a, last frost Apr 11
Questions
What growing zone is Portsmouth, RI?
Portsmouth is in USDA Plant Hardiness Zone 7a (average extreme winter low 0°F to 5°F), according to the USDA 2023 map.
When is the last frost in Portsmouth?
The average last spring frost (32°F) in Portsmouth is April 11. There is still a 10% chance of frost until April 22.
When can I plant tomatoes in Portsmouth?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 18 – Apr 25. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Tiverton, RI (USC00377581), 4.4 km (2.7 mi) from the city center, elevation 27 m, based on 18 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.