Frost dates for 59446Geraldine, MT
The average last spring frost in Geraldine is May 14 and the average first fall frost is September 26, giving a typical growing season of about 134 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 14
- Average first fall frost
- Sep 26
- Growing season
- 134 days
Safer after May 28 (1-in-10 risk)
Possible by Sep 13 (1-in-10 risk)
Last frost typically in 192 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 14 · May 28 · Jun 12 | Aug 31 · Sep 17 · Sep 29 | 112 days | 100% |
| Frost / freeze (32°F) | May 2 · May 14 · May 28 | Sep 13 · Sep 26 · Oct 7 | 134 days | 100% |
| Hard freeze (28°F) | Apr 17 · May 3 · May 17 | Sep 22 · Oct 4 · Oct 18 | 155 days | 100% |
Planting calendar for Geraldine
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 13 – Jun 19 |
| Tomatoes | Transplant outdoors | May 30 – Jun 6 |
| Peppers | Start seeds indoors | Apr 13 – May 14 |
| Peppers | Transplant outdoors | Jun 13 – Jul 14 |
| Eggplant | Start seeds indoors | Apr 30 – May 29 |
| Eggplant | Transplant outdoors | Jun 13 – Jul 14 |
| Cucumbers | Sow outdoors | Jun 13 – Jun 16 |
| Summer squash | Sow outdoors | May 30 – Jul 14 |
| Winter squash & pumpkins | Sow outdoors | Jun 13 – Jul 14 |
| Snap beans | Sow outdoors | May 30 – Jul 9 |
| Sweet corn | Sow outdoors | May 30 – Jun 6 |
| Watermelon & cantaloupe | Sow outdoors | Jun 13 – Jul 14 |
| Okra | Sow outdoors | Jun 6 – Jun 29 |
| Peas | Sow outdoors (spring) | Apr 13 – May 29 |
| Potatoes | Plant outdoors (spring) | Apr 13 – Jun 13 |
| Onions | Start seeds indoors (spring) | Mar 2 – Mar 29 |
| Onions | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (spring) | Mar 26 – Apr 29 |
| Broccoli | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (fall) | May 27 – Jun 6 |
| Broccoli | Transplant outdoors (fall) | Jun 26 – Jul 7 |
| Cabbage | Start seeds indoors (spring) | Mar 16 – Apr 13 |
| Cabbage | Transplant outdoors (spring) | Apr 13 – May 14 |
| Cabbage | Start seeds indoors (fall) | May 17 – Jun 16 |
| Cabbage | Transplant outdoors (fall) | Jun 16 – Jul 17 |
| Leaf lettuce | Sow outdoors (spring) | Apr 13 – Jun 29 |
| Leaf lettuce | Sow outdoors (fall) | Jun 16 – Aug 2 |
| Spinach | Sow outdoors (spring) | Apr 6 – May 20 |
| Spinach | Sow outdoors (fall) | Jul 3 – Aug 7 |
| Radishes | Sow outdoors (spring) | Apr 13 – Jun 3 |
| Radishes | Sow outdoors (fall) | Jun 16 – Aug 17 |
| Kale | Sow outdoors (spring) | Apr 30 – May 20 |
| Kale | Sow outdoors (fall) | Jun 9 – Jul 17 |
| Carrots | Sow outdoors (spring) | May 14 – Jun 29 |
| Carrots | Sow outdoors (fall) | May 17 – Jul 2 |
| Garlic | Plant outdoors (fall) | Sep 16 – Oct 17 |
Where these dates come from
ZIP code 59446 is matched to the NOAA station Geraldine, MT, 0.7 km away, at 3,145 ft elevation (34 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Geraldine, MT (used) | 3,145 ft | May 14 | Sep 26 |
| Shonkin 7 S, MT | 4,300 ft | May 24 | Sep 21 |
| Highwood 7 Ne, MT | 3,600 ft | May 7 | Oct 2 |
| Ft Benton, MT | 2,649 ft | May 15 | Sep 22 |
Frost dates near Geraldine
- Coffee Creek, MT 59424 · last Jun 1, first Sep 11
- Highwood, MT 59450 · last May 7, first Oct 2
- Geyser, MT 59447 · last May 22, first Sep 23
- Loma, MT 59460 · last May 20, first Sep 19
- Fort Benton, MT 59442 · last May 20, first Sep 19
- Denton, MT 59430 · last Jun 1, first Sep 11
- Raynesford, MT 59469 · last May 22, first Sep 23
- Stanford, MT 59479 · last May 28, first Sep 20
Frequently asked questions
- When is the last frost in Geraldine, MT?
- For ZIP code 59446, the average last spring frost (32°F) is May 14, based on NOAA 1991-2020 climate normals for the Geraldine, MT weather station. There is a 1-in-10 chance of a frost after May 28.
- When is the first frost in Geraldine, MT?
- The average first fall frost (32°F) is September 26. There is a 1-in-10 chance of frost by September 13, so tender plants are at risk from that point on.
- How long is the growing season in 59446?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 134 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.