Frost dates for 46321Munster, IN
The average last spring frost in Munster is April 23 and the average first fall frost is October 20, giving a typical growing season of about 179 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 23
- Average first fall frost
- Oct 20
- Growing season
- 179 days
Safer after May 11 (1-in-10 risk)
Possible by Oct 6 (1-in-10 risk)
Last frost typically in 172 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 20 · May 5 · May 24 | Sep 27 · Oct 10 · Oct 22 | 157 days | 100% |
| Frost / freeze (32°F) | Apr 9 · Apr 23 · May 11 | Oct 6 · Oct 20 · Nov 1 | 179 days | 100% |
| Hard freeze (28°F) | Mar 30 · Apr 12 · Apr 27 | Oct 18 · Oct 30 · Nov 15 | 202 days | 100% |
Planting calendar for Munster
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 | Mar 23 – May 29 |
| Tomatoes | Transplant outdoors | May 9 – Jun 30 |
| Peppers | Start seeds indoors | Mar 23 – Apr 23 |
| Peppers | Transplant outdoors | May 23 – Jun 23 |
| Eggplant | Start seeds indoors | Apr 9 – May 8 |
| Eggplant | Transplant outdoors | May 23 – Jun 23 |
| Cucumbers | Sow outdoors | May 23 – Jul 10 |
| Summer squash | Sow outdoors | May 9 – Jun 23 |
| Winter squash & pumpkins | Sow outdoors | May 23 – Jun 23 |
| Snap beans | Sow outdoors | May 9 – Aug 2 |
| Sweet corn | Sow outdoors | May 9 – Jun 30 |
| Watermelon & cantaloupe | Sow outdoors | May 23 – Jun 23 |
| Okra | Sow outdoors | May 16 – Jun 8 |
| Peas | Sow outdoors (spring) | Mar 23 – May 8 |
| Potatoes | Plant outdoors (spring) | Mar 23 – May 23 |
| Onions | Start seeds indoors (spring) | Feb 9 – Mar 8 |
| Onions | Transplant outdoors (spring) | Apr 9 – May 8 |
| Broccoli | Start seeds indoors (spring) | Mar 5 – Apr 8 |
| Broccoli | Transplant outdoors (spring) | Apr 9 – May 8 |
| Broccoli | Start seeds indoors (fall) | Jun 20 – Jun 30 |
| Broccoli | Transplant outdoors (fall) | Jul 20 – Jul 31 |
| Cabbage | Start seeds indoors (spring) | Feb 23 – Mar 23 |
| Cabbage | Transplant outdoors (spring) | Mar 23 – Apr 23 |
| Cabbage | Start seeds indoors (fall) | Jun 10 – Jul 10 |
| Cabbage | Transplant outdoors (fall) | Jul 10 – Aug 10 |
| Leaf lettuce | Sow outdoors (spring) | Mar 23 – Jun 8 |
| Leaf lettuce | Sow outdoors (fall) | Jul 10 – Aug 26 |
| Spinach | Sow outdoors (spring) | Mar 16 – Apr 29 |
| Spinach | Sow outdoors (fall) | Jul 27 – Aug 31 |
| Radishes | Sow outdoors (spring) | Mar 23 – May 13 |
| Radishes | Sow outdoors (fall) | Jul 10 – Sep 10 |
| Kale | Sow outdoors (spring) | Apr 9 – Apr 29 |
| Kale | Sow outdoors (fall) | Jul 3 – Aug 10 |
| Carrots | Sow outdoors (spring) | Apr 23 – Jun 8 |
| Carrots | Sow outdoors (fall) | Jun 10 – Jul 26 |
| Garlic | Plant outdoors (fall) | Oct 10 – Nov 10 |
Where these dates come from
ZIP code 46321 is matched to the NOAA station Park Forest, IL, 16.3 km away, at 710 ft elevation (93 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Park Forest, IL (used) | 710 ft | Apr 23 | Oct 20 |
| Chicago Midway Ap 3Sw, IL | 620 ft | Apr 10 | Nov 1 |
| Lowell, IN | 665 ft | Apr 29 | Oct 16 |
| Chicago Midway Ap, IL | 612 ft | Apr 11 | Oct 31 |
Frost dates near Munster
- Hammond, IN 46324 · last Apr 23, first Oct 20
- Highland, IN 46322 · last Apr 23, first Oct 20
- Lansing, IL 60438 · last Apr 23, first Oct 20
- Griffith, IN 46319 · last Apr 23, first Oct 20
- Dyer, IN 46311 · last Apr 23, first Oct 20
- Schererville, IN 46375 · last Apr 23, first Oct 20
- Calumet City, IL 60409 · last Apr 23, first Oct 20
- Gary, IN 46406 · last Apr 23, first Oct 20
Frequently asked questions
- When is the last frost in Munster, IN?
- For ZIP code 46321, the average last spring frost (32°F) is April 23, based on NOAA 1991-2020 climate normals for the Park Forest, IL weather station. There is a 1-in-10 chance of a frost after May 11.
- When is the first frost in Munster, IN?
- The average first fall frost (32°F) is October 20. There is a 1-in-10 chance of frost by October 6, so tender plants are at risk from that point on.
- How long is the growing season in 46321?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 179 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.