USDA Hardiness Zone 5a
Frost Dates for 59041 — Joliet, Montana
Averages from Joliet, Mt US, the nearest reporting station, 4.9 miles away.
Plant tender crops after May 29, and expect the first autumn freeze around September 15. That leaves about 107 frost-free days.
- Last spring frost
- May 29
- First fall frost
- September 15
- Growing season
- 107 days
- Hardiness zone
- 5a
50% probability
50% probability
frost-free
-20 to -15°F annual low
- First snow
- October 11
- Last snow
- April 19
- Winters with snow
- 100%
- Snow per year
- 50.9"
median, 1991–2020
median, 1991–2020
29 of 29 observed
NOAA normal
When it snows in Joliet, Montana
The first measurable snow (0.1 inch or more) in Joliet, Montana usually arrives around October 11, and the last of the season around April 19. Those are the middle dates across the winters of 1991–2020 at Joliet, Mt US: half of years saw snow earlier, half later. Every one of those winters saw snow.
For a gardener, snow matters less than frost: a light snow on frozen ground changes nothing, while a hard frost on an unprotected bed ends the season. Use the frost dates above for planting and the snow dates for getting hoses drained, mulch down and tender pots indoors.
Planting calendar for 59041
| When | What to do |
|---|---|
| March 20 – April 3 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 3 – April 17 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 1 – May 15 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| May 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 23 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 1 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 15 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 29 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Joliet, Montana are past their last freeze. Harvest before September 15, which leaves roughly 107 frost-free days.
ZIP 59041 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.