Harrisburg, IL Frost Dates & Growing Season

The two dates every Harrisburg garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
Apr 7
~50% chance of frost after
First fall frost
Oct 26
~50% chance of frost before
Growing season
202 days
frost-free stretch
USDA zone
≈ 7a
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Mar 21 Apr 7 Apr 25
First fall frost Nov 8 Oct 26 Oct 10
Hard freeze (28°F), median last Mar 26 · first Nov 6

Computed from NOAA 1991–2020 climate normals at the HARRISBURG station. "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Harrisburg

Computed from Harrisburg's own frost dates. Click any crop for the full zone-7 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Feb 10 – Feb 24 Apr 14 – Apr 21
🫑 Peppers Jan 27 – Feb 10 Apr 21 – Apr 28
🥬 Lettuce Feb 24 – Mar 10 Mar 10 – Mar 24 Mar 10 – Apr 7
🫛 Peas Feb 24 – Mar 10
🥕 Carrots Mar 17 – Apr 7
🥦 Broccoli Feb 17 – Mar 3 Mar 17 – Mar 31
🥬 Kale Feb 24 – Mar 10 Mar 10 – Mar 24 Mar 10 – Mar 24
🥒 Cucumbers Mar 10 – Mar 17 Apr 14 – Apr 21 Apr 14 – Apr 21
🥒 Zucchini Mar 10 – Mar 17 Apr 14 – Apr 21 Apr 14 – Apr 21
🫘 Green Beans (Bush) Apr 14 – Apr 21
🌽 Sweet Corn Apr 14 – Apr 21
🌿 Basil Feb 24 – Mar 10 Apr 14 – Apr 21 Apr 21 – Apr 28
🧄 Garlic Fall: Sep 14 – Oct 12

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Harrisburg's dates automatically after a lookup.

Reading the season in Harrisburg

With roughly 202 frost-free days, Harrisburg gardens fit long-season crops — melons, winter squash, sweet potatoes — with room left for spring and fall rounds of greens and roots. The first frost around Oct 26 is late enough that fall planting is a full second season, not an afterthought.

Frequently asked questions

When is the last frost in Harrisburg, IL?

The average last spring frost in Harrisburg is around Apr 7, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Harrisburg, IL?

The average first fall frost in Harrisburg arrives around Oct 26. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Harrisburg?

About 202 frost-free days on average, from Apr 7 to Oct 26. That comfortably fits long-season crops like melons and winter squash, plus spring and fall plantings of cool-season vegetables.

What USDA zone is Harrisburg in?

USDA zone 7a on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.