ZIP 59401 Zone 4b
Montana · USDA zone 4b, average annual extreme minimum -25°F to -20°F.
Nearest qualified station: GREAT FALLS 16ST, MT US (USC00243749), 1.6 miles from the Census ZCTA internal point for this ZIP.
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Last 32°F in spring
NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.
| Probability | Date | How to read it |
|---|---|---|
| 90% | April 23 | Earlier date. A last 32°F on or after this day is common. |
| 50% | May 6 | Median. |
| 10% | May 19 | Later date. A last 32°F on or after this day is uncommon. |
First 32°F in fall
NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.
| Probability | Date | How to read it |
|---|---|---|
| 10% | September 17 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | October 1 | Median. |
| 90% | October 16 | Later date. A first 32°F on or before this day is common. |
32°F growing-season length
Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.
| Probability the season is at least this long | Days |
|---|---|
| 10% | 166 |
| 50% | 147 |
| 90% | 129 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | May 8 | April 24 | April 7 |
| First, on or before | September 25 | October 11 | October 29 |
| Season at least | 193 days | 171 days | 149 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | June 1 | May 19 | May 6 |
| First, on or before | September 7 | September 21 | October 3 |
| Season at least | 142 days | 124 days | 105 days |
Station GREAT FALLS 16ST, MT US (USC00243749). Completeness flag R, 14 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 1068.3 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.