Frost dates for 67738Grinnell, KS
The average last spring frost in Grinnell is May 6 and the average first fall frost is October 9, giving a typical growing season of about 156 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 6
- Average first fall frost
- Oct 9
- Growing season
- 156 days
Safer after May 18 (1-in-10 risk)
Possible by Sep 27 (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) | May 3 · May 14 · May 27 | Sep 18 · Oct 1 · Oct 11 | 138 days | 100% |
| Frost / freeze (32°F) | Apr 22 · May 6 · May 18 | Sep 27 · Oct 9 · Oct 21 | 156 days | 100% |
| Hard freeze (28°F) | Apr 12 · Apr 27 · May 10 | Oct 4 · Oct 18 · Oct 29 | 172 days | 100% |
Planting calendar for Grinnell
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 5 – Jun 11 |
| Tomatoes | Transplant outdoors | May 22 – Jun 19 |
| Peppers | Start seeds indoors | Apr 5 – May 6 |
| Peppers | Transplant outdoors | Jun 5 – Jul 6 |
| Eggplant | Start seeds indoors | Apr 22 – May 21 |
| Eggplant | Transplant outdoors | Jun 5 – Jul 6 |
| Cucumbers | Sow outdoors | Jun 5 – Jun 29 |
| Summer squash | Sow outdoors | May 22 – Jul 6 |
| Winter squash & pumpkins | Sow outdoors | Jun 5 – Jul 6 |
| Snap beans | Sow outdoors | May 22 – Jul 22 |
| Sweet corn | Sow outdoors | May 22 – Jun 19 |
| Watermelon & cantaloupe | Sow outdoors | Jun 5 – Jul 6 |
| Okra | Sow outdoors | May 29 – Jun 21 |
| Peas | Sow outdoors (spring) | Apr 5 – May 21 |
| Potatoes | Plant outdoors (spring) | Apr 5 – Jun 5 |
| Onions | Start seeds indoors (spring) | Feb 22 – Mar 21 |
| Onions | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (spring) | Mar 18 – Apr 21 |
| Broccoli | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (fall) | Jun 9 – Jun 19 |
| Broccoli | Transplant outdoors (fall) | Jul 9 – Jul 20 |
| Cabbage | Start seeds indoors (spring) | Mar 8 – Apr 5 |
| Cabbage | Transplant outdoors (spring) | Apr 5 – May 6 |
| Cabbage | Start seeds indoors (fall) | May 30 – Jun 29 |
| Cabbage | Transplant outdoors (fall) | Jun 29 – Jul 30 |
| Leaf lettuce | Sow outdoors (spring) | Apr 5 – Jun 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 29 – Aug 15 |
| Spinach | Sow outdoors (spring) | Mar 29 – May 12 |
| Spinach | Sow outdoors (fall) | Jul 16 – Aug 20 |
| Radishes | Sow outdoors (spring) | Apr 5 – May 26 |
| Radishes | Sow outdoors (fall) | Jun 29 – Aug 30 |
| Kale | Sow outdoors (spring) | Apr 22 – May 12 |
| Kale | Sow outdoors (fall) | Jun 22 – Jul 30 |
| Carrots | Sow outdoors (spring) | May 6 – Jun 21 |
| Carrots | Sow outdoors (fall) | May 30 – Jul 15 |
| Garlic | Plant outdoors (fall) | Sep 29 – Oct 30 |
Where these dates come from
ZIP code 67738 is matched to the NOAA station Oakley 4W, KS, 24.6 km away, at 3,102 ft elevation (192 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Oakley 4W, KS (used) | 3,102 ft | May 6 | Oct 9 |
| Oakley 19 Ssw, KS | 2,870 ft | Apr 28 | Oct 15 |
| Hoxie, KS | 2,713 ft | Apr 20 | Oct 20 |
| Quinter, KS | 2,672 ft | Apr 24 | Oct 18 |
Frost dates near Grinnell
- Grainfield, KS 67737 · last Apr 24, first Oct 18
- Oakley, KS 67748 · last May 6, first Oct 9
- Gove, KS 67736 · last Apr 24, first Oct 18
- Park, KS 67751 · last Apr 24, first Oct 18
- Hoxie, KS 67740 · last Apr 20, first Oct 20
- Monument, KS 67747 · last May 6, first Oct 9
- Quinter, KS 67752 · last Apr 24, first Oct 18
- Rexford, KS 67753 · last Apr 20, first Oct 20
Frequently asked questions
- When is the last frost in Grinnell, KS?
- For ZIP code 67738, the average last spring frost (32°F) is May 6, based on NOAA 1991-2020 climate normals for the Oakley 4W, KS weather station. There is a 1-in-10 chance of a frost after May 18.
- When is the first frost in Grinnell, KS?
- The average first fall frost (32°F) is October 9. There is a 1-in-10 chance of frost by September 27, so tender plants are at risk from that point on.
- How long is the growing season in 67738?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 156 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.