Frost dates for 55398Zimmerman, MN
The average last spring frost in Zimmerman is May 7 and the average first fall frost is September 28, giving a typical growing season of about 144 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 7
- Average first fall frost
- Sep 28
- Growing season
- 144 days
Safer after May 22 (1-in-10 risk)
Possible by Sep 15 (1-in-10 risk)
Last frost typically in 189 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 4 · May 18 · Jun 3 | Sep 6 · Sep 20 · Oct 3 | 124 days | 100% |
| Frost / freeze (32°F) | Apr 24 · May 7 · May 22 | Sep 15 · Sep 28 · Oct 11 | 144 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 28 · May 12 | Sep 23 · Oct 8 · Oct 23 | 163 days | 100% |
Planting calendar for Zimmerman
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 6 – Jun 12 |
| Tomatoes | Transplant outdoors | May 23 – Jun 8 |
| Peppers | Start seeds indoors | Apr 6 – May 7 |
| Peppers | Transplant outdoors | Jun 6 – Jul 7 |
| Eggplant | Start seeds indoors | Apr 23 – May 22 |
| Eggplant | Transplant outdoors | Jun 6 – Jul 7 |
| Cucumbers | Sow outdoors | Jun 6 – Jun 18 |
| Summer squash | Sow outdoors | May 23 – Jul 7 |
| Winter squash & pumpkins | Sow outdoors | Jun 6 – Jul 7 |
| Snap beans | Sow outdoors | May 23 – Jul 11 |
| Sweet corn | Sow outdoors | May 23 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 6 – Jul 7 |
| Okra | Sow outdoors | May 30 – Jun 22 |
| Peas | Sow outdoors (spring) | Apr 6 – May 22 |
| Potatoes | Plant outdoors (spring) | Apr 6 – Jun 6 |
| Onions | Start seeds indoors (spring) | Feb 23 – Mar 22 |
| Onions | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (spring) | Mar 19 – Apr 22 |
| Broccoli | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 9 – Apr 6 |
| Cabbage | Transplant outdoors (spring) | Apr 6 – May 7 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 6 – Jun 22 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Mar 30 – May 13 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 6 – May 27 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | Apr 23 – May 13 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 7 – Jun 22 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 55398 is matched to the NOAA station Santiago 3 E, MN, 16.6 km away, at 1,010 ft elevation (22 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Santiago 3 E, MN (used) | 1,010 ft | May 7 | Sep 28 |
| Elk Rvr, MN | 880 ft | May 4 | Oct 5 |
| Cedar, MN | 907 ft | May 1 | Oct 7 |
| Cambridge, MN | 965 ft | May 2 | Oct 4 |
Frost dates near Zimmerman
- Princeton, MN 55371 · last May 7, first Sep 28
- Elk River, MN 55330 · last May 4, first Oct 5
- Big Lake, MN 55309 · last Apr 30, first Oct 9
- Saint Francis, MN 55070 · last May 1, first Oct 7
- Becker, MN 55308 · last May 7, first Sep 28
- Santiago, MN 55377 · last May 7, first Sep 28
- Albertville, MN 55301 · last Apr 30, first Oct 9
- Anoka, MN 55303 · last May 1, first Oct 7
Frequently asked questions
- When is the last frost in Zimmerman, MN?
- For ZIP code 55398, the average last spring frost (32°F) is May 7, based on NOAA 1991-2020 climate normals for the Santiago 3 E, MN weather station. There is a 1-in-10 chance of a frost after May 22.
- When is the first frost in Zimmerman, MN?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 15, so tender plants are at risk from that point on.
- How long is the growing season in 55398?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 144 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.