USDA Hardiness Zone 5a
Frost Dates for 59759 — Whitehall, Montana
Averages from Butte Bert Mooney Ap, Mt US, the nearest reporting station, 17.7 miles away.
Plant tender crops after June 13, and expect the first autumn freeze around September 5. That leaves about 83 frost-free days.
- Last spring frost
- June 13
- First fall frost
- September 5
- Growing season
- 83 days
- Hardiness zone
- 5a
50% probability
50% probability
frost-free
-20 to -15°F annual low
Planting calendar for 59759
| When | What to do |
|---|---|
| April 4 – April 18 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 18 – May 2 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 16 – May 30 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| June 13 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 13 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by August 22 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 5 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 13 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Whitehall, Montana are past their last freeze. Harvest before September 5, which leaves roughly 83 frost-free days.
ZIP 59759 sits in USDA hardiness zone 5a, meaning the average coldest night of the year falls between -20 to -15°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.