Frost dates for 55920Byron, MN
The average last spring frost in Byron is May 12 and the average first fall frost is September 28, giving a typical growing season of about 139 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 12
- Average first fall frost
- Sep 28
- Growing season
- 139 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 14 (1-in-10 risk)
Last frost typically in 190 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 8 · May 22 · Jun 4 | Sep 5 · Sep 19 · Oct 2 | 120 days | 100% |
| Frost / freeze (32°F) | Apr 29 · May 12 · May 25 | Sep 14 · Sep 28 · Oct 10 | 139 days | 100% |
| Hard freeze (28°F) | Apr 18 · May 2 · May 15 | Sep 22 · Oct 5 · Oct 18 | 156 days | 100% |
Planting calendar for Byron
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 11 – Jun 17 |
| Tomatoes | Transplant outdoors | May 28 – Jun 8 |
| Peppers | Start seeds indoors | Apr 11 – May 12 |
| Peppers | Transplant outdoors | Jun 11 – Jul 12 |
| Eggplant | Start seeds indoors | Apr 28 – May 27 |
| Eggplant | Transplant outdoors | Jun 11 – Jul 12 |
| Cucumbers | Sow outdoors | Jun 11 – Jun 18 |
| Summer squash | Sow outdoors | May 28 – Jul 12 |
| Winter squash & pumpkins | Sow outdoors | Jun 11 – Jul 12 |
| Snap beans | Sow outdoors | May 28 – Jul 11 |
| Sweet corn | Sow outdoors | May 28 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 11 – Jul 12 |
| Okra | Sow outdoors | Jun 4 – Jun 27 |
| Peas | Sow outdoors (spring) | Apr 11 – May 27 |
| Potatoes | Plant outdoors (spring) | Apr 11 – Jun 11 |
| Onions | Start seeds indoors (spring) | Feb 28 – Mar 27 |
| Onions | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (spring) | Mar 24 – Apr 27 |
| Broccoli | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 14 – Apr 11 |
| Cabbage | Transplant outdoors (spring) | Apr 11 – May 12 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 11 – Jun 27 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Apr 4 – May 18 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 11 – Jun 1 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | Apr 28 – May 18 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 12 – Jun 27 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 55920 is matched to the NOAA station Byron 4North, MN, 6 km away, at 1,041 ft elevation (170 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Byron 4North, MN (used) | 1,041 ft | May 12 | Sep 28 |
| Rochester Intl Ap, MN | 1,304 ft | Apr 30 | Oct 6 |
| Zumbrota, MN | 970 ft | May 9 | Sep 30 |
| Grand Meadow, MN | 1,350 ft | May 6 | Oct 1 |
Frost dates near Byron
- Rochester, MN 55903 · last May 12, first Sep 28
- Kasson, MN 55944 · last May 12, first Sep 28
- Mantorville, MN 55955 · last May 12, first Sep 28
- Oronoco, MN 55960 · last May 12, first Sep 28
- Dodge Center, MN 55927 · last May 12, first Sep 28
- Pine Island, MN 55963 · last May 9, first Sep 30
- Hayfield, MN 55940 · last Apr 30, first Oct 6
- Stewartville, MN 55976 · last Apr 30, first Oct 6
Frequently asked questions
- When is the last frost in Byron, MN?
- For ZIP code 55920, the average last spring frost (32°F) is May 12, based on NOAA 1991-2020 climate normals for the Byron 4North, MN weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Byron, MN?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 14, so tender plants are at risk from that point on.
- How long is the growing season in 55920?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 139 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.