Frost Dates for Decatur, IL 62521
Last spring frost April 18 · First fall frost October 17 · 182 frost-free days · USDA Zone 6a
ZIP 62521 has about 32,700 people, the largest of 4 ZIP codes in Decatur.
Long season: 182 frost-free days. Spring frost risk spans April 2–May 4 (32 days). Fall frost risk spans September 29–November 4 (36 days).
Frost probability for 62521
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | May 4 | April 18 | April 2 |
| Fall (first frost) | September 29 | October 17 | November 4 |
Dates come from NOAA 1971–2000 freeze probabilities at WINDSOR (50.0 km away); the 50% date is the median year.
Frost dates by ZIP code in Decatur, IL
| ZIP | Last spring frost (50%) | First fall frost (50%) | Zone |
|---|---|---|---|
| 62521 | April 18 | October 17 | 6a |
| 62526 | April 18 | October 12 | 6a |
| 62522 | April 18 | October 12 | 6a |
| 62523 | April 18 | October 12 | 6a |
Which crops fit a 182-day season in Decatur
In Decatur (182 frost-free days, a long season), 30 of 56 planner crops fit outright, 25 get two plantings, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Mar 14 | May 2–May 9 | 140 | fits: 80 days to maturity, 140 available after May 2. | Jun 17 |
| Pepper | Mar 7 | May 2–May 9 | 140 | fits: 75 days to maturity, 140 available after May 2. | Jun 22 |
| Lettuce | Feb 21 | Mar 21–Mar 28 | 217 | two-plantings: Plant Mar 21 and again by Aug 26; both mature before Oct 24. | Aug 26 |
| Carrots | — | Mar 28–Apr 4 | 224 | fits: 70 days to maturity, 224 available after Mar 28. | Aug 15 |
| Cucumber | Mar 28 | May 2–May 9 | 154 | two-plantings: Plant May 2 and again by Jul 21; both mature before Oct 3. | Jul 21 |
| Beans | — | Apr 25–May 9 | 168 | two-plantings: Plant Apr 25 and again by Jul 28; both mature before Oct 10. | Jul 28 |
| Peas | — | Feb 21–May 2 | 245 | fits: 65 days to maturity, 245 available after Feb 21. | Aug 6 |
| Zucchini | Apr 4 | May 2–May 9 | 154 | two-plantings: Plant May 2 and again by Jul 26; both mature before Oct 3. | Jul 26 |
| Onion | Jan 24 | Mar 21–Apr 4 | 217 | fits: 100 days to maturity, 217 available after Mar 21. | — |
| Spinach | — | Feb 21–Apr 11 | 259 | two-plantings: Plant Feb 21 and again by Sep 14; both mature before Nov 7. | Sep 14 |
| Kale | Feb 7 | Mar 21–Apr 4 | 231 | two-plantings: Plant Mar 21 and again by Aug 30; both mature before Nov 7. | Aug 30 |
| Broccoli | Feb 21 | Mar 21–Apr 4 | 217 | fits: 80 days to maturity, 217 available after Mar 21. | Jul 22 |
| Cabbage | Feb 21 | Mar 21–Apr 4 | 231 | fits: 70 days to maturity, 231 available after Mar 21. | Aug 15 |
| Radish | — | Feb 21–May 16 | 245 | two-plantings: Plant Feb 21 and again by Sep 15; both mature before Oct 24. | Sep 15 |
| Beets | — | Feb 21–May 16 | 245 | two-plantings: Plant Feb 21 and again by Aug 16; both mature before Oct 24. | Aug 16 |
| Potatoes | — | Apr 4–Apr 11 | 203 | fits: 90 days to maturity, 203 available after Apr 4. | — |
| Garlic | — | Oct 17 | 287 | overwinter: Plant Oct 17 to Nov 7; harvest the following summer. | Nov 7 |
| Strawberry | — | Mar 14–May 9 | 238 | perennial: A perennial: plant Mar 14; it fruits from the following year and keeps producing for several years. | — |
| Corn | Mar 21 | Apr 25–May 2 | 154 | fits: 75 days to maturity, 154 available after Apr 25. | Jun 29 |
| Pumpkin | Apr 4 | May 2–May 2 | 147 | fits: 100 days to maturity, 147 available after May 2. | Jun 4 |
| Cauliflower | Mar 7 | Apr 11–Apr 25 | 196 | fits: 75 days to maturity, 196 available after Apr 11. | Jul 27 |
| Swiss Chard | Feb 21 | Apr 4–Apr 4 | 203 | two-plantings: Plant Apr 4 and again by Aug 16; both mature before Oct 24. | Aug 16 |
| Arugula | — | Feb 21–May 16 | 259 | two-plantings: Plant Feb 21 and again by Sep 14; both mature before Nov 7. | Sep 14 |
| Brussel Sprouts | Feb 21 | Mar 21–Apr 4 | 231 | fits: 100 days to maturity, 231 available after Mar 21. | Jul 16 |
| Butternut Squash | Apr 4 | May 2–May 9 | 147 | fits: 100 days to maturity, 147 available after May 2. | Jun 4 |
| Eggplant | Feb 28 | May 2–May 9 | 140 | fits: 70 days to maturity, 140 available after May 2. | Jun 27 |
| Okra | Mar 21 | Apr 25–May 2 | 161 | two-plantings: Plant Apr 25 and again by Jul 26; both mature before Oct 3. | Jul 26 |
| Basil | Mar 14 | May 9–May 9 | 147 | two-plantings: Plant May 9 and again by Jul 21; both mature before Oct 3. | Jul 21 |
| Cilantro | — | Mar 21–Apr 11 | 217 | two-plantings: Plant Mar 21 and again by Aug 21; both mature before Oct 24. | Aug 21 |
| Parsley | Feb 7 | Apr 25–May 2 | 182 | fits: 70 days to maturity, 182 available after Apr 25. | Aug 1 |
| Celery | Feb 7 | Apr 25–May 9 | 182 | fits: 120 days to maturity, 182 available after Apr 25. | Jun 12 |
| Scallions | Feb 7 | Mar 21–Apr 4 | 231 | two-plantings: Plant Mar 21 and again by Aug 25; both mature before Nov 7. | Aug 25 |
| Turnip | — | Mar 21–Apr 4 | 231 | two-plantings: Plant Mar 21 and again by Sep 4; both mature before Nov 7. | Sep 4 |
| Kohlrabi | — | Mar 7–Mar 21 | 245 | two-plantings: Plant Mar 7 and again by Aug 30; both mature before Nov 7. | Aug 30 |
| Bok Choy | Mar 21 | Apr 11–Apr 18 | 196 | two-plantings: Plant Apr 11 and again by Aug 26; both mature before Oct 24. | Aug 26 |
| Collards | Feb 7 | Mar 21–Apr 4 | 231 | two-plantings: Plant Mar 21 and again by Aug 25; both mature before Nov 7. | Aug 25 |
| Cantaloupe | Apr 4 | May 2–May 9 | 140 | fits: 85 days to maturity, 140 available after May 2. | Jun 12 |
| Chives | Jan 24 | Apr 25–May 2 | 196 | fits: 90 days to maturity, 196 available after Apr 25. | — |
| Dill | — | Feb 21–May 16 | 245 | two-plantings: Plant Feb 21 and again by Aug 16; both mature before Oct 24. | Aug 16 |
| Oregano | Feb 7 | Apr 25–May 2 | 196 | fits: 80 days to maturity, 196 available after Apr 25. | — |
| Rosemary | Jan 24 | Apr 25–May 2 | 182 | fits: 80 days to maturity, 182 available after Apr 25. | — |
| Sage | Feb 21 | Apr 25–May 2 | 196 | fits: 75 days to maturity, 196 available after Apr 25. | — |
| Thyme | Feb 7 | Apr 25–May 2 | 196 | fits: 90 days to maturity, 196 available after Apr 25. | — |
| Calendula | Mar 7 | Apr 4–Apr 18 | 203 | two-plantings: Plant Apr 4 and again by Aug 21; both mature before Oct 24. | Aug 21 |
| Cosmos | Mar 21 | Apr 18–May 2 | 168 | two-plantings: Plant Apr 18 and again by Jul 21; both mature before Oct 3. | Jul 21 |
| Lavender | Jan 24 | Apr 18–May 2 | 203 | fits: 90 days to maturity, 203 available after Apr 18. | — |
| Marigolds | Mar 7 | Apr 18–Apr 25 | 168 | two-plantings: Plant Apr 18 and again by Jul 31; both mature before Oct 3. | Jul 31 |
| Melons | Apr 4 | May 2–May 9 | 140 | fits: 85 days to maturity, 140 available after May 2. | Jun 12 |
| Mint | — | Apr 18–May 2 | 203 | fits: 90 days to maturity, 203 available after Apr 18. | — |
| Nasturtiums | Mar 21 | Apr 18–Apr 25 | 168 | two-plantings: Plant Apr 18 and again by Jul 26; both mature before Oct 3. | Jul 26 |
| Pole Beans | — | Apr 25–May 9 | 161 | fits: 65 days to maturity, 161 available after Apr 25. | Jul 16 |
| Spaghetti Squash | Apr 4 | May 2–May 9 | 147 | fits: 90 days to maturity, 147 available after May 2. | Jun 14 |
| Sunflowers | — | Apr 18–May 2 | 168 | fits: 70 days to maturity, 168 available after Apr 18. | Jul 11 |
| Tomatillos | Feb 21 | Apr 25–May 2 | 147 | fits: 75 days to maturity, 147 available after Apr 25. | Jun 22 |
| Watermelon | Apr 4 | Apr 25–May 2 | 147 | fits: 80 days to maturity, 147 available after Apr 25. | Jun 17 |
| Yellow Squash | Apr 4 | May 2–May 9 | 154 | two-plantings: Plant May 2 and again by Jul 26; both mature before Oct 3. | Jul 26 |
| Zinnias | Mar 21 | Apr 18–May 2 | 168 | two-plantings: Plant Apr 18 and again by Jul 21; both mature before Oct 3. | Jul 21 |
Month by month in Decatur
| Month | What to do |
|---|---|
| January | Start indoors: Chives (Jan 24), Lavender (Jan 24), Onion (Jan 24), Rosemary (Jan 24). |
| February | Start indoors: Celery (Feb 7), Collards (Feb 7), Kale (Feb 7), Oregano (Feb 7), Parsley (Feb 7), Scallions (Feb 7), +9 more. Direct sow from: Arugula (Feb 21), Beets (Feb 21), Dill (Feb 21), Peas (Feb 21), Radish (Feb 21), Spinach (Feb 21). |
| March | Start indoors: Calendula (Mar 7), Cauliflower (Mar 7), Marigolds (Mar 7), Pepper (Mar 7), Basil (Mar 14), Tomato (Mar 14), +7 more. Direct sow from: Kohlrabi (Mar 7), Cilantro (Mar 21), Turnip (Mar 21), Carrots (Mar 28). Transplant from: Broccoli (Mar 21), Brussel Sprouts (Mar 21), Cabbage (Mar 21), Collards (Mar 21), Kale (Mar 21), Lettuce (Mar 21), +2 more. Plant: Strawberry (Mar 14). |
| April | Start indoors: Butternut Squash (Apr 4), Cantaloupe (Apr 4), Melons (Apr 4), Pumpkin (Apr 4), Spaghetti Squash (Apr 4), Watermelon (Apr 4), +2 more. Direct sow from: Potatoes (Apr 4), Sunflowers (Apr 18), Beans (Apr 25), Pole Beans (Apr 25). Transplant from: Calendula (Apr 4), Swiss Chard (Apr 4), Bok Choy (Apr 11), Cauliflower (Apr 11), Cosmos (Apr 18), Lavender (Apr 18), +15 more. Last frost around April 18. |
| May | Transplant from: Butternut Squash (May 2), Cantaloupe (May 2), Cucumber (May 2), Eggplant (May 2), Melons (May 2), Pepper (May 2), +6 more. |
| June | Last sowing dates: Butternut Squash (Jun 4), Pumpkin (Jun 4), Cantaloupe (Jun 12), Celery (Jun 12), Melons (Jun 12), Spaghetti Squash (Jun 14), +6 more. |
| July | Last sowing dates: Sunflowers (Jul 11), Brussel Sprouts (Jul 16), Pole Beans (Jul 16), Basil (Jul 21), Cosmos (Jul 21), Cucumber (Jul 21), +9 more. |
| August | Last sowing dates: Parsley (Aug 1), Peas (Aug 6), Cabbage (Aug 15), Carrots (Aug 15), Beets (Aug 16), Dill (Aug 16), +9 more. |
| September | Last sowing dates: Turnip (Sep 4), Arugula (Sep 14), Spinach (Sep 14), Radish (Sep 15). |
| October | Direct sow from: Garlic (Oct 17). First frost around October 17. |
| November | Last sowing dates: Garlic (Nov 7). |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Decatur, IL (ZIP 62521)?
The median last spring frost date for Decatur, IL (ZIP code 62521) is around April 18. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before April 2; one in ten it runs past May 4.
What is the first fall frost date in Decatur, IL?
The median first fall frost date for Decatur, IL is around October 17. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around September 29 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Decatur, IL?
The frost-free growing season in Decatur is about 182 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Decatur (182 frost-free days, a long season), 30 of 56 planner crops fit outright, 25 get two plantings, 1 crop is perennial.
What USDA hardiness zone is Decatur, IL?
Decatur, IL is in USDA hardiness zone 6a (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Decatur, IL?
Start tomatoes indoors Mar 14 and plant out May 2 in Decatur. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Decatur?
Two: plant Mar 21 and again by Aug 26; both mature before Oct 24.
When do I plant garlic in Decatur?
Oct 17 to Nov 7; it overwinters and is ready the following summer.
Can I get two tomato crops in Decatur?
Yes: plant out May 2 for a summer crop, and set out a second round of transplants by Jun 17 for a fall crop.
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