Plan your vegetable garden in Illinois

All the statistical weather information you need to prepare a bulletproof plan for your garden in Illinois

Temperature range in Illinois

Illinois has temperatures ranging from -19°F to 97°F, with approximately 192 frost free days.

Illinois has 159 days with average temperature range from 50°F to 90°F that are suitable for growing warm season vegetables and 114 days with average temperature range from 40°F to 80°F that are suitable for growing cool season vegetables

Chart displaying weekly air temperature in Illinois — Illinois air temperature chart based on weather statistics from 2019 to 2023

Total frost free days (after last frost and before first frost)	192
Total days suitable to grow warm season vegetables	159
Total days suitable to grow cool season vegetables	114
Day with highest recorded temperature in past 4 years	August 24: 97°F
Day with lowest recorded temperature in past 4 years	January 30: -19°F
First expected frost date	October 31
Last expected frost date	April 22

Notable temperature facts for gardening in Illinois

Warm season vegetables you can grow in Illinois

Chart displaying days suitable for growing warm season vegetables in Illinois — Days suitable for growing warm season vegetables in Illinois

Warm season vegetables can be planted in Illinois after May 14 when air temperatures are consistently above 50°F (10°C) and soil temperature is above 50°F (10°C)

Good temperature range for warm season vegetables is between 50°F and 90°F. With warm season vegetables it is important to wait until all conditions are optimal, because sudden temperature drop can stun new vegetable growth, this way delaying overall harvest.

Warm season vegetables that can be planted directly into soil in Illinois

Cucumber

Summer squash

Winter squash

Sweet corn

Eggplant

Bell Pepper

Okra

Tomato

Tomatillo

True Melon

Watermelon

Warm season vegetables that need to be started indoors before transplanting outdoors in Illinois

Chayote

Chilli Pepper

Cool season vegetables you can grow in Illinois

Chart displaying days suitable for growing cool season vegetables in Illinois — Days suitable for growing cool season vegetables in Illinois

Cool season vegetables can be planted in Illinois after April 22 when average air temperature is consistently above 40°F (4°C) and soil temperature is above 45°F (7°C)

Good temperature range for cool season vegetables is between 40°F and 80°F. With cool season vegetables it is important to avoid high air temperatures because exposure to high temperatures is most likely to stun growth, cause bitterness and encourage premature bolting in some plants. Plan your cool vegetable planting so they are harvested before hot weather stretch, provide them with additional shading.

Cool season vegetables that can be planted directly into soil in Illinois

Beets

Turnip

Chives

Coriander

Cool season vegetables that need to be started indoors before transplanting outdoors in Illinois

Arugula

Carrot

Kale

Radish

Spinach

Swiss chard

Cauliflower

Rhubarb

Rutabaga

Parsley

Endive

Artichoke

Parsnip

Kohlrabi

Table with days suitable to grow vegetables in Illinois

Tolerable temperature range for cool season vegetables: 40°F to 80°F

Tolerable temperature range for warm season vegetables: 50°F to 90°F

	Week	Average temperature	Possible min and max temperature	Suitable for cool season vegetables	Suitable for warm season vegetables
1	January 01 - January 03	29°F to 42°F	6°F to 58°F
2	January 04 - January 10	26°F to 40°F	0°F to 57°F
3	January 11 - January 17	27°F to 39°F	9°F to 55°F
4	January 18 - January 24	20°F to 35°F	-2°F to 46°F
5	January 25 - January 31	16°F to 31°F	-19°F to 43°F
6	February 01 - February 07	22°F to 38°F	-3°F to 58°F
7	February 08 - February 14	19°F to 34°F	-6°F to 56°F
8	February 15 - February 21	20°F to 39°F	-5°F to 57°F
9	February 22 - February 28	28°F to 44°F	12°F to 59°F
10	March 01 - March 07	29°F to 49°F	0°F to 68°F
11	March 08 - March 14	34°F to 51°F	12°F to 67°F
12	March 15 - March 21	34°F to 52°F	17°F to 70°F
13	March 22 - March 28	38°F to 54°F	26°F to 69°F
14	March 29 - April 04	38°F to 58°F	26°F to 77°F
15	April 05 - April 11	45°F to 64°F	32°F to 77°F	TRUE
16	April 12 - April 18	41°F to 60°F	28°F to 77°F	TRUE
17	April 19 - April 25	44°F to 62°F	29°F to 80°F	TRUE
18	April 26 - May 02	47°F to 65°F	35°F to 80°F	TRUE
19	May 03 - May 09	49°F to 67°F	40°F to 81°F	TRUE
20	May 10 - May 16	52°F to 70°F	33°F to 87°F	TRUE	TRUE
21	May 17 - May 23	57°F to 74°F	47°F to 84°F	TRUE	TRUE
22	May 24 - May 30	60°F to 77°F	44°F to 86°F	TRUE	TRUE
23	May 31 - June 06	62°F to 80°F	52°F to 89°F	TRUE	TRUE
24	June 07 - June 13	62°F to 80°F	52°F to 91°F	TRUE	TRUE
25	June 14 - June 20	64°F to 83°F	53°F to 93°F		TRUE
26	June 21 - June 27	67°F to 83°F	54°F to 93°F		TRUE
27	June 28 - July 04	69°F to 85°F	58°F to 91°F		TRUE
28	July 05 - July 11	69°F to 85°F	61°F to 93°F		TRUE
29	July 12 - July 18	68°F to 84°F	63°F to 90°F		TRUE
30	July 19 - July 25	69°F to 86°F	61°F to 93°F		TRUE
31	July 26 - August 01	69°F to 85°F	60°F to 94°F		TRUE
32	August 02 - August 08	67°F to 83°F	56°F to 90°F		TRUE
33	August 09 - August 15	68°F to 83°F	62°F to 91°F		TRUE
34	August 16 - August 22	67°F to 83°F	58°F to 91°F		TRUE
35	August 23 - August 29	69°F to 85°F	60°F to 97°F		TRUE
36	August 30 - September 05	65°F to 81°F	55°F to 90°F		TRUE
37	September 06 - September 12	64°F to 80°F	56°F to 89°F	TRUE	TRUE
38	September 13 - September 19	62°F to 80°F	53°F to 87°F	TRUE	TRUE
39	September 20 - September 26	60°F to 76°F	48°F to 91°F	TRUE	TRUE
40	September 27 - October 03	59°F to 75°F	44°F to 87°F	TRUE	TRUE
41	October 04 - October 10	53°F to 70°F	38°F to 82°F	TRUE	TRUE
42	October 11 - October 17	49°F to 66°F	37°F to 79°F	TRUE
43	October 18 - October 24	48°F to 64°F	33°F to 78°F	TRUE
44	October 25 - October 31	44°F to 55°F	29°F to 72°F	TRUE
45	November 01 - November 07	40°F to 58°F	24°F to 73°F	TRUE
46	November 08 - November 14	39°F to 54°F	11°F to 74°F
47	November 15 - November 21	35°F to 50°F	18°F to 65°F
48	November 22 - November 28	33°F to 47°F	18°F to 57°F
49	November 29 - December 05	32°F to 47°F	22°F to 60°F
50	December 06 - December 12	32°F to 46°F	18°F to 61°F
51	December 13 - December 19	30°F to 41°F	15°F to 66°F
52	December 20 - December 26	29°F to 44°F	-8°F to 61°F
53	December 27 - December 31	31°F to 45°F	10°F to 60°F

Table with days suitable to grow vegetables in Illinois

Counties in Illinois

For more precise weather statisctics and planting information, please select a County.