Lanark, IL frost dates
Last spring frostMay 2median date
First fall frostOct 7median date
Growing season158 daysfrost-free
Hardiness zone5aZone 5a
How Lanark compares
- In 8 years out of 10, the last spring frost in Lanark falls between April 18 and May 18, a 30-day window. The first fall frost falls between September 24 and October 20.
- The median last frost is 15 days later than the Illinois median of Apr 17.
- Its 158-day growing season is among the shortest of the 1,287 Illinois places with a regular frost season.
- The last frost is typical for zone 5a, where the median is May 3.
- The weather station records an average of 155 nights a year at or below 32°F.
- Compared with Rockford, IL, 64 km away, the last frost here is 8 days later than there and the growing season is 18 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 18 |
| 50% (median) | May 2 |
| 10% (safe for tender plants) | May 18 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 24 |
| 50% (median) | October 7 |
| 90% (late) | October 20 |
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 Lanark, IL
Lanark, IL frost dates — last frost May 2, first frost Oct 7, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 7 to Feb 21Transplant outside: Apr 4 to Apr 18
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Mar 7 to Mar 21Transplant outside: May 9 to May 23
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Sow outdoors: Apr 4 to May 9Plant for fall: Aug 12 to Sep 9
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 4 to Apr 18Sow outdoors: Apr 4 to Apr 18Plant for fall: Jul 29 to Aug 19
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 21 to Apr 4Transplant outside: May 23 to Jun 6Sow outdoors: May 23 to Jun 6
Start indoors: Mar 21 to Apr 4Transplant outside: May 9 to May 23
Sow outdoors: Mar 21 to Apr 11Plant for fall: Jul 15 to Aug 5
Sow outdoors: Mar 21 to Apr 11Plant for fall: Aug 12 to Sep 2
Sow outdoors: Mar 28 to May 9Plant for fall: Aug 26 to Sep 16
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 23Sow outdoors: May 9 to May 23Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23Plant for fall: Jul 29 to Aug 12
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 30
Sow outdoors: Apr 11 to May 9Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 11 to May 9Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 11 to May 2
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 18 to May 9Plant for fall: Aug 12 to Sep 2
Sow outdoors: May 9 to May 30Plant for fall: Jul 22 to Aug 5
Sow outdoors: May 9 to May 23
Transplant outside: May 16 to Jun 6
Plant for fall: Sep 23 to Oct 28
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Lanark, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 7 – Feb 21 | Apr 4 – Apr 18 | — | — |
| Peppers | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Eggplant | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Tomatoes | Mar 7 – Mar 21 | May 9 – May 23 | — | — |
| Lettuce | Mar 7 – Mar 21 | Apr 11 – Apr 25 | Apr 4 – May 9 | Aug 12 – Sep 9 |
| Kale | Mar 7 – Mar 21 | Apr 4 – Apr 18 | Apr 4 – Apr 18 | Jul 29 – Aug 19 |
| Broccoli | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jul 1 – Jul 22 |
| Cabbage | Mar 7 – Mar 21 | Apr 11 – Apr 25 | — | Jul 1 – Jul 22 |
| Cauliflower | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jul 1 – Jul 22 |
| Okra | Mar 21 – Apr 4 | May 23 – Jun 6 | May 23 – Jun 6 | — |
| Basil | Mar 21 – Apr 4 | May 9 – May 23 | — | — |
| Peas | — | — | Mar 21 – Apr 11 | Jul 15 – Aug 5 |
| Spinach | — | — | Mar 21 – Apr 11 | Aug 12 – Sep 2 |
| Radishes | — | — | Mar 28 – May 9 | Aug 26 – Sep 16 |
| Cucumbers | Apr 4 – Apr 11 | May 16 – May 23 | May 9 – May 23 | Jul 22 – Aug 5 |
| Zucchini & Summer Squash | Apr 4 – Apr 11 | — | May 9 – May 23 | Jul 29 – Aug 12 |
| Winter Squash & Pumpkins | Apr 4 – Apr 11 | — | May 9 – May 23 | — |
| Melons & Watermelon | Apr 4 – Apr 11 | May 16 – May 30 | — | — |
| Carrots | — | — | Apr 11 – May 9 | Jul 15 – Jul 29 |
| Beets | — | — | Apr 11 – May 9 | Jul 29 – Aug 12 |
| Potatoes | — | — | Apr 11 – May 2 | — |
| Swiss Chard | — | — | Apr 18 – May 16 | Jul 29 – Aug 12 |
| Cilantro | — | — | Apr 18 – May 9 | Aug 12 – Sep 2 |
| Green Beans | — | — | May 9 – May 30 | Jul 22 – Aug 5 |
| Sweet Corn | — | — | May 9 – May 23 | — |
| Sweet Potatoes | — | May 16 – Jun 6 | — | — |
| 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 Mt Carroll, IL weather station, 13 km away (elevation 640 ft (195 m)).
Frost dates near Lanark
- Shannon Apr 29 · Oct 7
- Chadwick May 2 · Oct 7
- Mount Carroll May 2 · Oct 7
- Milledgeville Apr 29 · Oct 7
- Pearl City Apr 26 · Oct 13
- Forreston Apr 29 · Oct 7
- Baileyville Apr 26 · Oct 13
- Polo Apr 29 · Oct 7
- Thomson Apr 13 · Oct 26
- Kent Apr 27 · Oct 9
Frequently asked questions
When is the last frost in Lanark, IL?
The median last spring frost in Lanark, IL is May 2. There is still about a 10% chance of frost after May 18, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Lanark, IL?
The median first fall frost is October 7, with about a 10% chance of frost before September 24.
How long is the growing season in Lanark, IL?
About 158 days between the median last spring frost and first fall frost.
What planting zone is Lanark, IL?
Lanark, IL is in USDA hardiness zone 5a.