Rock Falls, IA frost dates
Last spring frostApr 29median date
First fall frostOct 7median date
Growing season161 daysfrost-free
Hardiness zone5aZone 5a
How Rock Falls compares
- In 8 years out of 10, the last spring frost in Rock Falls falls between April 14 and May 9, a 25-day window. The first fall frost falls between September 25 and October 21.
- The median last frost is 1 day later than the Iowa median of Apr 28.
- Its 161-day growing season is longer than 28% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is 4 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 161 nights a year at or below 32°F.
- Compared with Waterloo, IA, 101 km away, the last frost here is 2 days later than there and the growing season is 5 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 14 |
| 50% (median) | April 29 |
| 10% (safe for tender plants) | May 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 25 |
| 50% (median) | October 7 |
| 90% (late) | October 21 |
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 Rock Falls, IA
Rock Falls, IA frost dates — last frost Apr 29, first frost Oct 7, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 4 to Feb 18Transplant outside: Apr 1 to Apr 15
Start indoors: Feb 18 to Mar 4Transplant outside: May 13 to May 27
Start indoors: Feb 18 to Mar 4Transplant outside: May 13 to May 27
Start indoors: Mar 4 to Mar 18Transplant outside: May 6 to May 20
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 1 to May 6Plant for fall: Aug 12 to Sep 9
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 1 to Apr 15Sow outdoors: Apr 1 to Apr 15Plant for fall: Jul 29 to Aug 19
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 8 to Apr 22Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 18 to Apr 1Transplant outside: May 20 to Jun 3Sow outdoors: May 20 to Jun 3
Start indoors: Mar 18 to Apr 1Transplant outside: May 6 to May 20
Sow outdoors: Mar 18 to Apr 8Plant for fall: Jul 15 to Aug 5
Sow outdoors: Mar 18 to Apr 8Plant for fall: Aug 12 to Sep 2
Sow outdoors: Mar 25 to May 6Plant for fall: Aug 26 to Sep 16
Start indoors: Apr 1 to Apr 8Transplant outside: May 13 to May 20Sow outdoors: May 6 to May 20Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 1 to Apr 8Sow outdoors: May 6 to May 20Plant for fall: Jul 29 to Aug 12
Start indoors: Apr 1 to Apr 8Sow outdoors: May 6 to May 20
Start indoors: Apr 1 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Apr 8 to May 6Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 8 to May 6Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 8 to Apr 29
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 15 to May 6Plant for fall: Aug 12 to Sep 2
Sow outdoors: May 6 to May 27Plant for fall: Jul 22 to Aug 5
Sow outdoors: May 6 to May 20
Transplant outside: May 13 to Jun 3
Plant for fall: Sep 23 to Oct 28
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Rock Falls, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 4 – Feb 18 | Apr 1 – Apr 15 | — | — |
| Peppers | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Eggplant | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Tomatoes | Mar 4 – Mar 18 | May 6 – May 20 | — | — |
| Lettuce | Mar 4 – Mar 18 | Apr 8 – Apr 22 | Apr 1 – May 6 | Aug 12 – Sep 9 |
| Kale | Mar 4 – Mar 18 | Apr 1 – Apr 15 | Apr 1 – Apr 15 | Jul 29 – Aug 19 |
| Broccoli | Mar 4 – Mar 18 | Apr 15 – Apr 29 | — | Jul 1 – Jul 22 |
| Cabbage | Mar 4 – Mar 18 | Apr 8 – Apr 22 | — | Jul 1 – Jul 22 |
| Cauliflower | Mar 4 – Mar 18 | Apr 15 – Apr 29 | — | Jul 1 – Jul 22 |
| Okra | Mar 18 – Apr 1 | May 20 – Jun 3 | May 20 – Jun 3 | — |
| Basil | Mar 18 – Apr 1 | May 6 – May 20 | — | — |
| Peas | — | — | Mar 18 – Apr 8 | Jul 15 – Aug 5 |
| Spinach | — | — | Mar 18 – Apr 8 | Aug 12 – Sep 2 |
| Radishes | — | — | Mar 25 – May 6 | Aug 26 – Sep 16 |
| Cucumbers | Apr 1 – Apr 8 | May 13 – May 20 | May 6 – May 20 | Jul 22 – Aug 5 |
| Zucchini & Summer Squash | Apr 1 – Apr 8 | — | May 6 – May 20 | Jul 29 – Aug 12 |
| Winter Squash & Pumpkins | Apr 1 – Apr 8 | — | May 6 – May 20 | — |
| Melons & Watermelon | Apr 1 – Apr 8 | May 13 – May 27 | — | — |
| Carrots | — | — | Apr 8 – May 6 | Jul 15 – Jul 29 |
| Beets | — | — | Apr 8 – May 6 | Jul 29 – Aug 12 |
| Potatoes | — | — | Apr 8 – Apr 29 | — |
| Swiss Chard | — | — | Apr 15 – May 13 | Jul 29 – Aug 12 |
| Cilantro | — | — | Apr 15 – May 6 | Aug 12 – Sep 2 |
| Green Beans | — | — | May 6 – May 27 | Jul 22 – Aug 5 |
| Sweet Corn | — | — | May 6 – May 20 | — |
| Sweet Potatoes | — | May 13 – Jun 3 | — | — |
| Garlic | — | — | — | Sep 23 – Oct 28 |
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 Mason City, IA weather station, 10 km away (elevation 1,106 ft (337 m)).
Frost dates near Rock Falls
- Plymouth Apr 29 · Oct 7
- Nora Springs Apr 29 · Oct 7
- Mason City Apr 29 · Oct 7
- Grafton May 4 · Oct 4
- Manly Apr 29 · Oct 7
- Rudd Apr 30 · Oct 9
- Kensett May 4 · Oct 4
- Rockford Apr 30 · Oct 6
- Osage Apr 30 · Oct 9
- Carpenter May 4 · Oct 4
Frequently asked questions
When is the last frost in Rock Falls, IA?
The median last spring frost in Rock Falls, IA is April 29. There is still about a 10% chance of frost after May 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Rock Falls, IA?
The median first fall frost is October 7, with about a 10% chance of frost before September 25.
How long is the growing season in Rock Falls, IA?
About 161 days between the median last spring frost and first fall frost.
What planting zone is Rock Falls, IA?
Rock Falls, IA is in USDA hardiness zone 5a.