USDA Hardiness Zone 6b
Frost Dates for 83871 — Troy, Idaho
Averages from Potlatch 3 Nne, Id US, the nearest reporting station, 15.5 miles away.
Plant tender crops after May 15, and expect the first autumn freeze around September 21. That leaves about 126 frost-free days.
- Last spring frost
- May 15
- First fall frost
- September 21
- Growing season
- 126 days
- Hardiness zone
- 6b
50% probability
50% probability
frost-free
-5 to 0°F annual low
Planting calendar for 83871
| When | What to do |
|---|---|
| March 6 – March 20 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| March 20 – April 3 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| April 17 – May 1 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| May 15 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 29 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 7 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 21 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after May 15 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Troy, Idaho are past their last freeze. Harvest before September 21, which leaves roughly 126 frost-free days.
ZIP 83871 sits in USDA hardiness zone 6b, meaning the average coldest night of the year falls between -5 to 0°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.