Frost dates for 51603Shenandoah, IA
The average last spring frost in Shenandoah is April 20 and the average first fall frost is October 17, giving a typical growing season of about 179 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 20
- Average first fall frost
- Oct 17
- Growing season
- 179 days
Safer after May 3 (1-in-10 risk)
Possible by Oct 1 (1-in-10 risk)
Last frost typically in 175 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 17 · Apr 30 · May 11 | Sep 23 · Oct 6 · Oct 19 | 160 days | 100% |
| Frost / freeze (32°F) | Apr 5 · Apr 20 · May 3 | Oct 1 · Oct 17 · Oct 29 | 179 days | 100% |
| Hard freeze (28°F) | Mar 27 · Apr 9 · Apr 23 | Oct 13 · Oct 26 · Nov 7 | 199 days | 100% |
Planting calendar for Shenandoah
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 20 – May 26 |
| Tomatoes | Transplant outdoors | May 6 – Jun 27 |
| Peppers | Start seeds indoors | Mar 20 – Apr 20 |
| Peppers | Transplant outdoors | May 20 – Jun 20 |
| Eggplant | Start seeds indoors | Apr 6 – May 5 |
| Eggplant | Transplant outdoors | May 20 – Jun 20 |
| Cucumbers | Sow outdoors | May 20 – Jul 7 |
| Summer squash | Sow outdoors | May 6 – Jun 20 |
| Winter squash & pumpkins | Sow outdoors | May 20 – Jun 20 |
| Snap beans | Sow outdoors | May 6 – Jul 30 |
| Sweet corn | Sow outdoors | May 6 – Jun 27 |
| Watermelon & cantaloupe | Sow outdoors | May 20 – Jun 20 |
| Okra | Sow outdoors | May 13 – Jun 5 |
| Peas | Sow outdoors (spring) | Mar 20 – May 5 |
| Potatoes | Plant outdoors (spring) | Mar 20 – May 20 |
| Onions | Start seeds indoors (spring) | Feb 6 – Mar 5 |
| Onions | Transplant outdoors (spring) | Apr 6 – May 5 |
| Broccoli | Start seeds indoors (spring) | Mar 2 – Apr 5 |
| Broccoli | Transplant outdoors (spring) | Apr 6 – May 5 |
| Broccoli | Start seeds indoors (fall) | Jun 17 – Jun 27 |
| Broccoli | Transplant outdoors (fall) | Jul 17 – Jul 28 |
| Cabbage | Start seeds indoors (spring) | Feb 20 – Mar 20 |
| Cabbage | Transplant outdoors (spring) | Mar 20 – Apr 20 |
| Cabbage | Start seeds indoors (fall) | Jun 7 – Jul 7 |
| Cabbage | Transplant outdoors (fall) | Jul 7 – Aug 7 |
| Leaf lettuce | Sow outdoors (spring) | Mar 20 – Jun 5 |
| Leaf lettuce | Sow outdoors (fall) | Jul 7 – Aug 23 |
| Spinach | Sow outdoors (spring) | Mar 13 – Apr 26 |
| Spinach | Sow outdoors (fall) | Jul 24 – Aug 28 |
| Radishes | Sow outdoors (spring) | Mar 20 – May 10 |
| Radishes | Sow outdoors (fall) | Jul 7 – Sep 7 |
| Kale | Sow outdoors (spring) | Apr 6 – Apr 26 |
| Kale | Sow outdoors (fall) | Jun 30 – Aug 7 |
| Carrots | Sow outdoors (spring) | Apr 20 – Jun 5 |
| Carrots | Sow outdoors (fall) | Jun 7 – Jul 23 |
| Garlic | Plant outdoors (fall) | Oct 7 – Nov 7 |
Where these dates come from
ZIP code 51603 is matched to the NOAA station Shenandoah, IA, 1.5 km away, at 999 ft elevation (18 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Shenandoah, IA (used) | 999 ft | Apr 20 | Oct 17 |
| Sidney 1Sse, IA | 1,140 ft | Apr 19 | Oct 19 |
| Red Oak, IA | 1,040 ft | Apr 24 | Oct 13 |
| Clarinda, IA | 980 ft | Apr 25 | Oct 11 |
Frost dates near Shenandoah
- Shenandoah, IA 51601 · last Apr 20, first Oct 17
- Farragut, IA 51639 · last Apr 20, first Oct 17
- Essex, IA 51638 · last Apr 20, first Oct 17
- Imogene, IA 51645 · last Apr 20, first Oct 17
- Coin, IA 51636 · last Apr 20, first Oct 17
- Northboro, IA 51647 · last Apr 20, first Oct 17
- Yorktown, IA 51656 · last Apr 25, first Oct 11
- Randolph, IA 51649 · last Apr 20, first Oct 17
Frequently asked questions
- When is the last frost in Shenandoah, IA?
- For ZIP code 51603, the average last spring frost (32°F) is April 20, based on NOAA 1991-2020 climate normals for the Shenandoah, IA weather station. There is a 1-in-10 chance of a frost after May 3.
- When is the first frost in Shenandoah, IA?
- The average first fall frost (32°F) is October 17. There is a 1-in-10 chance of frost by October 1, so tender plants are at risk from that point on.
- How long is the growing season in 51603?
- 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.