USDA Hardiness Zone 4b
Frost Dates for 59722 — Deer Lodge, Montana
Averages from Elliston, Mt US, the nearest reporting station, 18.6 miles away.
Plant tender crops after June 9, and expect the first autumn freeze around September 8. That leaves about 91 frost-free days.
- Last spring frost
- June 9
- First fall frost
- September 8
- Growing season
- 91 days
- Hardiness zone
- 4b
50% probability
50% probability
frost-free
-25 to -20°F annual low
Planting calendar for 59722
| When | What to do |
|---|---|
| March 31 – April 14 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 14 – April 28 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 12 – May 26 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| June 9 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 16 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by August 25 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 8 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 June 9 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Deer Lodge, Montana are past their last freeze. Harvest before September 8, which leaves roughly 91 frost-free days.
ZIP 59722 sits in USDA hardiness zone 4b, meaning the average coldest night of the year falls between -25 to -20°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.