Lawn & Garden • Illinois Planting Dates • Updated October 29, 2026

When to Plant Tomatoes in Illinois: Dates, Soil Temps and Tips

Explore related guides: When to start seeds in Illinois · When to plant tomatoes in Minnesota · When to plant tomatoes in Iowa · Soil test kits · When to plant tomatoes in Wisconsin.

A warm week in late April makes every Illinois gardener want to plant tomatoes, but cold nights and chilly soil can stunt young plants even without a frost. This guide explains when to plant tomatoes in Illinois for the north, central and southern parts of the state, the soil and air temperatures University of Illinois Extension recommends waiting for, and how to give transplants a strong start.

When to plant tomatoes in Illinois: the short answer

In central Illinois, plant tomatoes on or after Mother’s Day, around mid-May, the rule of thumb Illinois Extension educators use. Southern Illinois can plant about two weeks earlier, in early May, and northern Illinois, including the Chicago area, about two weeks later, in mid to late May. Before planting, wait until nights are consistently in the 50s°F and soil has warmed to at least the mid-50s, ideally 60°F.

Tomato planting dates by region

Why so much later than the median freeze? Illinois Extension notes that in central Illinois a frost can still happen until about May 7 to 12, and one Extension educator points out there is still about a 10 percent chance of frost on May 15. The Illinois State Climatologist recommends adding about two weeks to the average date for tender plants. Start seeds indoors 6 to 8 weeks before your planting date; see our Illinois seed starting calendar.

Why waiting pays off

• Tomatoes need warm soil and nights. Illinois Extension says tomatoes need soil temperatures in the mid-50s°F and minimum air temperatures above 45°F; another Extension educator recommends nighttime temperatures consistently in the 50s before warm-season plants go out.
• Cold above freezing still hurts. Temperatures well above freezing can still stunt transplants and slow them for weeks.
• Later can be faster. An Illinois Extension educator planted tomatoes and peppers on May 15, May 22 and May 31 and watched the May 31 planting outgrow the earlier ones, because it went into warmer conditions.

How to plant tomatoes in Illinois

1. Check the soil with a thermometer 2 to 4 inches deep in the morning. Dark soils and raised beds warm faster than light soils, as Illinois Extension notes.
2. Harden off transplants for 7 to 10 days, starting in shade and wind shelter.
3. Plant on a cloudy day or in the evening to reduce transplant stress.
4. Bury the stem deep, up to the first set of leaves; tomatoes root along the buried stem.
5. Add cages or stakes now so you do not damage roots later.
6. Water deeply, then mulch once soil is warm, and water evenly through summer to reduce blossom end rot.
7. Keep frost cloth ready through mid-May, especially in northern Illinois.

Tools for planting tomatoes

All five were listed as sold by Amazon.com when checked on October 29, 2026. Check the current listing before you buy.

To know when soil is ready: Taylor Soil Thermometer

A stainless steel probe that reads below the surface, with a dial that shows optimal planting ranges. It tells you when your soil has reached the temperatures Illinois Extension recommends.

For a late cold snap: Amazon Basics Plant Covers, 10 x 30 ft

A breathable frost cloth for the light frosts that can still show up in mid-May. Cover plants in the evening and uncover them the next morning.

For support: Happygrill Adjustable Tomato Cages, 60 in, 3 Pack

Tall PE-coated metal cages with adjustable rings plus clips and ties. Put them in at planting time so you do not disturb roots later.

For tying to stakes: VELCRO Brand Adjustable Plant Ties, 75 ft

Soft, reusable ties that hold stems to stakes without cutting into them.

For steady watering: Gilmour 50 ft Flat Soaker Hose

A flat soaker hose that waters the roots, not the leaves, through hot Illinois summers. Steady moisture helps prevent blossom end rot.

Conclusion

Plant tomatoes in Illinois in early May in the south, on or after Mother’s Day in central Illinois, and in mid to late May in the north. Let the soil and nights decide: soil in the mid-50s to 60°F, nights consistently in the 50s, and no frost in the forecast. A week’s patience often gives you a faster, healthier crop.

FAQs

Is Mother’s Day a good time to plant tomatoes in Illinois?
In central Illinois, yes. Illinois Extension educators often recommend planting warm-season crops on or after Mother’s Day. In northern Illinois, waiting another week or two is safer.

When should I plant tomatoes in Chicago?
Mid to late May, about two weeks later than central Illinois, once nights stay in the 50s°F.

What soil temperature do tomatoes need?
Illinois Extension says tomatoes need soil in the mid-50s°F and minimum air temperatures above 45°F; 60°F soil is even better.

Can it still frost in May in Illinois?
Yes. In central Illinois a frost can occur until about May 7 to 12, and there is roughly a 10 percent chance on May 15.

When should I start tomato seeds in Illinois?
About 6 to 8 weeks before planting out: mid to late March in central Illinois, earlier in the south and later in the north.

Is it bad to plant tomatoes too early?
Often, yes. Cold soil and cool nights stunt transplants, and later plantings frequently catch up and outgrow early ones.

Sources and review scope

This guide was prepared on October 29, 2026 from the following sources and from the product listings on Amazon.com. Homingwell did not perform hands-on testing.

• University of Illinois Extension – Warm season plants and frost-free date
• University of Illinois Extension – Give your garden a rest; tend to Mom this weekend
• University of Illinois Extension – When to plant
• WAND TV with Illinois Extension – Spring gardening tips
• Illinois State Climatologist – Spring frost in Illinois

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