Frost dates for 55040Isanti, MN
The average last spring frost in Isanti is May 2 and the average first fall frost is October 4, giving a typical growing season of about 153 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 2
- Average first fall frost
- Oct 4
- Growing season
- 153 days
Safer after May 20 (1-in-10 risk)
Possible by Sep 20 (1-in-10 risk)
Last frost typically in 184 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) | Apr 29 · May 13 · May 28 | Sep 11 · Sep 26 · Oct 10 | 133 days | 100% |
| Frost / freeze (32°F) | Apr 17 · May 2 · May 20 | Sep 20 · Oct 4 · Oct 19 | 153 days | 100% |
| Hard freeze (28°F) | Apr 6 · Apr 21 · May 6 | Sep 28 · Oct 15 · Nov 3 | 175 days | 100% |
Planting calendar for Isanti
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 1 – Jun 7 |
| Tomatoes | Transplant outdoors | May 18 – Jun 14 |
| Peppers | Start seeds indoors | Apr 1 – May 2 |
| Peppers | Transplant outdoors | Jun 1 – Jul 2 |
| Eggplant | Start seeds indoors | Apr 18 – May 17 |
| Eggplant | Transplant outdoors | Jun 1 – Jul 2 |
| Cucumbers | Sow outdoors | Jun 1 – Jun 24 |
| Summer squash | Sow outdoors | May 18 – Jul 2 |
| Winter squash & pumpkins | Sow outdoors | Jun 1 – Jul 2 |
| Snap beans | Sow outdoors | May 18 – Jul 17 |
| Sweet corn | Sow outdoors | May 18 – Jun 14 |
| Watermelon & cantaloupe | Sow outdoors | Jun 1 – Jul 2 |
| Okra | Sow outdoors | May 25 – Jun 17 |
| Peas | Sow outdoors (spring) | Apr 1 – May 17 |
| Potatoes | Plant outdoors (spring) | Apr 1 – Jun 1 |
| Onions | Start seeds indoors (spring) | Feb 18 – Mar 17 |
| Onions | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (spring) | Mar 14 – Apr 17 |
| Broccoli | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (fall) | Jun 4 – Jun 14 |
| Broccoli | Transplant outdoors (fall) | Jul 4 – Jul 15 |
| Cabbage | Start seeds indoors (spring) | Mar 4 – Apr 1 |
| Cabbage | Transplant outdoors (spring) | Apr 1 – May 2 |
| Cabbage | Start seeds indoors (fall) | May 25 – Jun 24 |
| Cabbage | Transplant outdoors (fall) | Jun 24 – Jul 25 |
| Leaf lettuce | Sow outdoors (spring) | Apr 1 – Jun 17 |
| Leaf lettuce | Sow outdoors (fall) | Jun 24 – Aug 10 |
| Spinach | Sow outdoors (spring) | Mar 25 – May 8 |
| Spinach | Sow outdoors (fall) | Jul 11 – Aug 15 |
| Radishes | Sow outdoors (spring) | Apr 1 – May 22 |
| Radishes | Sow outdoors (fall) | Jun 24 – Aug 25 |
| Kale | Sow outdoors (spring) | Apr 18 – May 8 |
| Kale | Sow outdoors (fall) | Jun 17 – Jul 25 |
| Carrots | Sow outdoors (spring) | May 2 – Jun 17 |
| Carrots | Sow outdoors (fall) | May 25 – Jul 10 |
| Garlic | Plant outdoors (fall) | Sep 24 – Oct 25 |
Where these dates come from
ZIP code 55040 is matched to the NOAA station Cambridge, MN, 9.8 km away, at 965 ft elevation (36 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Cambridge, MN (used) | 965 ft | May 2 | Oct 4 |
| Cedar, MN | 907 ft | May 1 | Oct 7 |
| Andover 1N, MN | 899 ft | May 5 | Oct 2 |
| Forest Lake 5Ne, MN | 905 ft | May 3 | Oct 5 |
Frost dates near Isanti
- Bethel, MN 55005 · last May 1, first Oct 7
- Cambridge, MN 55008 · last May 2, first Oct 4
- Saint Francis, MN 55070 · last May 1, first Oct 7
- Cedar, MN 55011 · last May 1, first Oct 7
- Stacy, MN 55079 · last May 3, first Oct 5
- Grandy, MN 55029 · last May 2, first Oct 4
- North Branch, MN 55056 · last May 19, first Sep 25
- Harris, MN 55032 · last May 2, first Oct 4
Frequently asked questions
- When is the last frost in Isanti, MN?
- For ZIP code 55040, the average last spring frost (32°F) is May 2, based on NOAA 1991-2020 climate normals for the Cambridge, MN weather station. There is a 1-in-10 chance of a frost after May 20.
- When is the first frost in Isanti, MN?
- The average first fall frost (32°F) is October 4. There is a 1-in-10 chance of frost by September 20, so tender plants are at risk from that point on.
- How long is the growing season in 55040?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 153 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.