Harpers Ferry, IA frost dates
Last spring frostApr 24median date
First fall frostOct 17median date
Growing season176 daysfrost-free
Hardiness zone5aZone 5a
How Harpers Ferry compares
- In 8 years out of 10, the last spring frost in Harpers Ferry falls between April 9 and May 8, a 29-day window. The first fall frost falls between October 4 and October 28.
- The median last frost is 4 days earlier than the Iowa median of Apr 28.
- Its 176-day growing season is longer than 84% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is 9 days earlier than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 134 nights a year at or below 32°F.
- Compared with La Crosse, WI, 76 km away, the last frost here is 3 days earlier than there and the growing season is 7 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 9 |
| 50% (median) | April 24 |
| 10% (safe for tender plants) | May 8 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 4 |
| 50% (median) | October 17 |
| 90% (late) | October 28 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Harpers Ferry, IA
Harpers Ferry, IA frost dates — last frost Apr 24, first frost Oct 17, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Jan 30 to Feb 13Transplant outside: Mar 27 to Apr 10
Start indoors: Feb 13 to Feb 27Transplant outside: May 8 to May 22
Start indoors: Feb 13 to Feb 27Transplant outside: May 8 to May 22
Start indoors: Feb 27 to Mar 13Transplant outside: May 1 to May 15
Start indoors: Feb 27 to Mar 13Transplant outside: Apr 3 to Apr 17Sow outdoors: Mar 27 to May 1Plant for fall: Aug 22 to Sep 19
Start indoors: Feb 27 to Mar 13Transplant outside: Mar 27 to Apr 10Sow outdoors: Mar 27 to Apr 10Plant for fall: Aug 8 to Aug 29
Start indoors: Feb 27 to Mar 13Transplant outside: Apr 10 to Apr 24Plant for fall: Jul 11 to Aug 1
Start indoors: Feb 27 to Mar 13Transplant outside: Apr 3 to Apr 17Plant for fall: Jul 11 to Aug 1
Start indoors: Feb 27 to Mar 13Transplant outside: Apr 10 to Apr 24Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 13 to Mar 27Transplant outside: May 15 to May 29Sow outdoors: May 15 to May 29
Start indoors: Mar 13 to Mar 27Transplant outside: May 1 to May 15
Sow outdoors: Mar 13 to Apr 3Plant for fall: Jul 25 to Aug 15
Sow outdoors: Mar 13 to Apr 3Plant for fall: Aug 22 to Sep 12
Sow outdoors: Mar 20 to May 1Plant for fall: Sep 5 to Sep 26
Start indoors: Mar 27 to Apr 3Transplant outside: May 8 to May 15Sow outdoors: May 1 to May 15Plant for fall: Aug 1 to Aug 15
Start indoors: Mar 27 to Apr 3Sow outdoors: May 1 to May 15Plant for fall: Aug 8 to Aug 22
Start indoors: Mar 27 to Apr 3Sow outdoors: May 1 to May 15
Start indoors: Mar 27 to Apr 3Transplant outside: May 8 to May 22
Sow outdoors: Apr 3 to May 1Plant for fall: Jul 25 to Aug 8
Sow outdoors: Apr 3 to May 1Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 3 to Apr 24
Sow outdoors: Apr 10 to May 8Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 10 to May 1Plant for fall: Aug 22 to Sep 12
Sow outdoors: May 1 to May 22Plant for fall: Aug 1 to Aug 15
Sow outdoors: May 1 to May 15
Transplant outside: May 8 to May 29
Plant for fall: Oct 3 to Nov 7
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Harpers Ferry, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 30 – Feb 13 | Mar 27 – Apr 10 | — | — |
| Peppers | Feb 13 – Feb 27 | May 8 – May 22 | — | — |
| Eggplant | Feb 13 – Feb 27 | May 8 – May 22 | — | — |
| Tomatoes | Feb 27 – Mar 13 | May 1 – May 15 | — | — |
| Lettuce | Feb 27 – Mar 13 | Apr 3 – Apr 17 | Mar 27 – May 1 | Aug 22 – Sep 19 |
| Kale | Feb 27 – Mar 13 | Mar 27 – Apr 10 | Mar 27 – Apr 10 | Aug 8 – Aug 29 |
| Broccoli | Feb 27 – Mar 13 | Apr 10 – Apr 24 | — | Jul 11 – Aug 1 |
| Cabbage | Feb 27 – Mar 13 | Apr 3 – Apr 17 | — | Jul 11 – Aug 1 |
| Cauliflower | Feb 27 – Mar 13 | Apr 10 – Apr 24 | — | Jul 11 – Aug 1 |
| Okra | Mar 13 – Mar 27 | May 15 – May 29 | May 15 – May 29 | — |
| Basil | Mar 13 – Mar 27 | May 1 – May 15 | — | — |
| Peas | — | — | Mar 13 – Apr 3 | Jul 25 – Aug 15 |
| Spinach | — | — | Mar 13 – Apr 3 | Aug 22 – Sep 12 |
| Radishes | — | — | Mar 20 – May 1 | Sep 5 – Sep 26 |
| Cucumbers | Mar 27 – Apr 3 | May 8 – May 15 | May 1 – May 15 | Aug 1 – Aug 15 |
| Zucchini & Summer Squash | Mar 27 – Apr 3 | — | May 1 – May 15 | Aug 8 – Aug 22 |
| Winter Squash & Pumpkins | Mar 27 – Apr 3 | — | May 1 – May 15 | — |
| Melons & Watermelon | Mar 27 – Apr 3 | May 8 – May 22 | — | — |
| Carrots | — | — | Apr 3 – May 1 | Jul 25 – Aug 8 |
| Beets | — | — | Apr 3 – May 1 | Aug 8 – Aug 22 |
| Potatoes | — | — | Apr 3 – Apr 24 | — |
| Swiss Chard | — | — | Apr 10 – May 8 | Aug 8 – Aug 22 |
| Cilantro | — | — | Apr 10 – May 1 | Aug 22 – Sep 12 |
| Green Beans | — | — | May 1 – May 22 | Aug 1 – Aug 15 |
| Sweet Corn | — | — | May 1 – May 15 | — |
| Sweet Potatoes | — | May 8 – May 29 | — | — |
| Garlic | — | — | — | Oct 3 – Nov 7 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Lynxville Dam, WI weather station, 11 km away (elevation 633 ft (193 m)).
Frost dates near Harpers Ferry
- Waterville May 2 · Oct 11
- Marquette Apr 28 · Oct 12
- Mc Gregor Apr 28 · Oct 12
- Monona May 1 · Oct 3
- Lansing May 2 · Oct 11
- Waukon May 2 · Oct 11
- Luana May 1 · Oct 3
- Farmersburg Apr 28 · Oct 12
- Saint Olaf May 8 · Oct 1
- Postville May 1 · Oct 3
Frequently asked questions
When is the last frost in Harpers Ferry, IA?
The median last spring frost in Harpers Ferry, IA is April 24. There is still about a 10% chance of frost after May 8, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Harpers Ferry, IA?
The median first fall frost is October 17, with about a 10% chance of frost before October 4.
How long is the growing season in Harpers Ferry, IA?
About 176 days between the median last spring frost and first fall frost.
What planting zone is Harpers Ferry, IA?
Harpers Ferry, IA is in USDA hardiness zone 5a.