Frost dates for 61046Lanark, IL
The average last spring frost in Lanark is April 29 and the average first fall frost is October 7, giving a typical growing season of about 161 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 29
- Average first fall frost
- Oct 7
- Growing season
- 161 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 23 (1-in-10 risk)
Last frost typically in 179 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 24 · May 9 · May 24 | Sep 14 · Sep 28 · Oct 11 | 142 days | 100% |
| Frost / freeze (32°F) | Apr 15 · Apr 29 · May 14 | Sep 23 · Oct 7 · Oct 22 | 161 days | 100% |
| Hard freeze (28°F) | Apr 4 · Apr 19 · May 5 | Oct 3 · Oct 19 · Nov 1 | 183 days | 100% |
Planting calendar for Lanark
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 29 – Jun 4 |
| Tomatoes | Transplant outdoors | May 15 – Jun 17 |
| Peppers | Start seeds indoors | Mar 29 – Apr 29 |
| Peppers | Transplant outdoors | May 29 – Jun 29 |
| Eggplant | Start seeds indoors | Apr 15 – May 14 |
| Eggplant | Transplant outdoors | May 29 – Jun 29 |
| Cucumbers | Sow outdoors | May 29 – Jun 27 |
| Summer squash | Sow outdoors | May 15 – Jun 29 |
| Winter squash & pumpkins | Sow outdoors | May 29 – Jun 29 |
| Snap beans | Sow outdoors | May 15 – Jul 20 |
| Sweet corn | Sow outdoors | May 15 – Jun 17 |
| Watermelon & cantaloupe | Sow outdoors | May 29 – Jun 29 |
| Okra | Sow outdoors | May 22 – Jun 14 |
| Peas | Sow outdoors (spring) | Mar 29 – May 14 |
| Potatoes | Plant outdoors (spring) | Mar 29 – May 29 |
| Onions | Start seeds indoors (spring) | Feb 15 – Mar 14 |
| Onions | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (spring) | Mar 11 – Apr 14 |
| Broccoli | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (fall) | Jun 7 – Jun 17 |
| Broccoli | Transplant outdoors (fall) | Jul 7 – Jul 18 |
| Cabbage | Start seeds indoors (spring) | Mar 1 – Mar 29 |
| Cabbage | Transplant outdoors (spring) | Mar 29 – Apr 29 |
| Cabbage | Start seeds indoors (fall) | May 28 – Jun 27 |
| Cabbage | Transplant outdoors (fall) | Jun 27 – Jul 28 |
| Leaf lettuce | Sow outdoors (spring) | Mar 29 – Jun 14 |
| Leaf lettuce | Sow outdoors (fall) | Jun 27 – Aug 13 |
| Spinach | Sow outdoors (spring) | Mar 22 – May 5 |
| Spinach | Sow outdoors (fall) | Jul 14 – Aug 18 |
| Radishes | Sow outdoors (spring) | Mar 29 – May 19 |
| Radishes | Sow outdoors (fall) | Jun 27 – Aug 28 |
| Kale | Sow outdoors (spring) | Apr 15 – May 5 |
| Kale | Sow outdoors (fall) | Jun 20 – Jul 28 |
| Carrots | Sow outdoors (spring) | Apr 29 – Jun 14 |
| Carrots | Sow outdoors (fall) | May 28 – Jul 13 |
| Garlic | Plant outdoors (fall) | Sep 27 – Oct 28 |
Where these dates come from
ZIP code 61046 is matched to the NOAA station Polo 5Nw, IL, 19.1 km away, at 856 ft elevation (26 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Polo 5Nw, IL (used) | 856 ft | Apr 29 | Oct 7 |
| Mt Carroll, IL | 640 ft | May 2 | Oct 7 |
| Freeport Waste Wtp, IL | 750 ft | Apr 26 | Oct 13 |
| Fulton L&D #13, IL | 592 ft | Apr 13 | Oct 26 |
Frost dates near Lanark
- Shannon, IL 61078 · last Apr 29, first Oct 7
- Chadwick, IL 61014 · last May 2, first Oct 7
- Mount Carroll, IL 61053 · last May 2, first Oct 7
- Milledgeville, IL 61051 · last Apr 29, first Oct 7
- Pearl City, IL 61062 · last Apr 27, first Oct 9
- Forreston, IL 61030 · last Apr 29, first Oct 7
- Baileyville, IL 61007 · last Apr 26, first Oct 13
- Polo, IL 61064 · last Apr 29, first Oct 7
Frequently asked questions
- When is the last frost in Lanark, IL?
- For ZIP code 61046, the average last spring frost (32°F) is April 29, based on NOAA 1991-2020 climate normals for the Polo 5Nw, IL weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Lanark, IL?
- The average first fall frost (32°F) is October 7. There is a 1-in-10 chance of frost by September 23, so tender plants are at risk from that point on.
- How long is the growing season in 61046?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 161 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.