Frost Dates for Alton, IL 62002
Last spring frost April 7 · First fall frost October 29 · 205 frost-free days · USDA Zone 7a
ZIP 62002 has about 29,500 people.
Long season: 205 frost-free days. Spring frost risk spans March 27–April 19 (23 days). Fall frost risk spans October 14–November 12 (29 days).
Frost probability for 62002
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | April 19 | April 7 | March 27 |
| Fall (first frost) | October 14 | October 29 | November 12 |
Dates come from NOAA 1971–2000 freeze probabilities at ST LOUIS LAMBERT INTL AP (29.7 km away); the 50% date is the median year.
Which crops fit a 205-day season in Alton
In Alton (205 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 3 | Apr 21–Apr 28 | 163 | fits: 80 days to maturity, 163 available after Apr 21. | Jun 29 |
| Pepper | Feb 24 | Apr 21–Apr 28 | 163 | fits: 75 days to maturity, 163 available after Apr 21. | Jul 4 |
| Lettuce | Feb 10 | Mar 10–Mar 17 | 240 | two-plantings: Plant Mar 10 and again by Sep 7; both mature before Nov 5. | Sep 7 |
| Carrots | — | Mar 17–Mar 24 | 247 | fits: 70 days to maturity, 247 available after Mar 17. | Aug 27 |
| Cucumber | Mar 17 | Apr 21–Apr 28 | 177 | two-plantings: Plant Apr 21 and again by Aug 2; both mature before Oct 15. | Aug 2 |
| Beans | — | Apr 14–Apr 28 | 191 | two-plantings: Plant Apr 14 and again by Aug 9; both mature before Oct 22. | Aug 9 |
| Peas | — | Feb 10–Apr 21 | 268 | fits: 65 days to maturity, 268 available after Feb 10. | Aug 18 |
| Zucchini | Mar 24 | Apr 21–Apr 28 | 177 | two-plantings: Plant Apr 21 and again by Aug 7; both mature before Oct 15. | Aug 7 |
| Onion | Jan 13 | Mar 10–Mar 24 | 240 | fits: 100 days to maturity, 240 available after Mar 10. | — |
| Spinach | — | Feb 10–Mar 31 | 282 | two-plantings: Plant Feb 10 and again by Sep 26; both mature before Nov 19. | Sep 26 |
| Kale | Jan 27 | Mar 10–Mar 24 | 254 | two-plantings: Plant Mar 10 and again by Sep 11; both mature before Nov 19. | Sep 11 |
| Broccoli | Feb 10 | Mar 10–Mar 24 | 240 | fits: 80 days to maturity, 240 available after Mar 10. | Aug 3 |
| Cabbage | Feb 10 | Mar 10–Mar 24 | 254 | fits: 70 days to maturity, 254 available after Mar 10. | Aug 27 |
| Radish | — | Feb 10–May 5 | 268 | two-plantings: Plant Feb 10 and again by Sep 27; both mature before Nov 5. | Sep 27 |
| Beets | — | Feb 10–May 5 | 268 | two-plantings: Plant Feb 10 and again by Aug 28; both mature before Nov 5. | Aug 28 |
| Potatoes | — | Mar 24–Mar 31 | 226 | fits: 90 days to maturity, 226 available after Mar 24. | — |
| Garlic | — | Oct 29 | 310 | overwinter: Plant Oct 29 to Nov 19; harvest the following summer. | Nov 19 |
| Strawberry | — | Mar 3–Apr 28 | 261 | perennial: A perennial: plant Mar 3; it fruits from the following year and keeps producing for several years. | — |
| Corn | Mar 10 | Apr 14–Apr 21 | 177 | fits: 75 days to maturity, 177 available after Apr 14. | Jul 11 |
| Pumpkin | Mar 24 | Apr 21–Apr 21 | 170 | fits: 100 days to maturity, 170 available after Apr 21. | Jun 16 |
| Cauliflower | Feb 24 | Mar 31–Apr 14 | 219 | fits: 75 days to maturity, 219 available after Mar 31. | Aug 8 |
| Swiss Chard | Feb 10 | Mar 24–Mar 24 | 226 | two-plantings: Plant Mar 24 and again by Aug 28; both mature before Nov 5. | Aug 28 |
| Arugula | — | Feb 10–May 5 | 282 | two-plantings: Plant Feb 10 and again by Sep 26; both mature before Nov 19. | Sep 26 |
| Brussel Sprouts | Feb 10 | Mar 10–Mar 24 | 254 | fits: 100 days to maturity, 254 available after Mar 10. | Jul 28 |
| Butternut Squash | Mar 24 | Apr 21–Apr 28 | 170 | fits: 100 days to maturity, 170 available after Apr 21. | Jun 16 |
| Eggplant | Feb 17 | Apr 21–Apr 28 | 163 | fits: 70 days to maturity, 163 available after Apr 21. | Jul 9 |
| Okra | Mar 10 | Apr 14–Apr 21 | 184 | two-plantings: Plant Apr 14 and again by Aug 7; both mature before Oct 15. | Aug 7 |
| Basil | Mar 3 | Apr 28–Apr 28 | 170 | two-plantings: Plant Apr 28 and again by Aug 2; both mature before Oct 15. | Aug 2 |
| Cilantro | — | Mar 10–Mar 31 | 240 | two-plantings: Plant Mar 10 and again by Sep 2; both mature before Nov 5. | Sep 2 |
| Parsley | Jan 27 | Apr 14–Apr 21 | 205 | fits: 70 days to maturity, 205 available after Apr 14. | Aug 13 |
| Celery | Jan 27 | Apr 14–Apr 28 | 205 | fits: 120 days to maturity, 205 available after Apr 14. | Jun 24 |
| Scallions | Jan 27 | Mar 10–Mar 24 | 254 | two-plantings: Plant Mar 10 and again by Sep 6; both mature before Nov 19. | Sep 6 |
| Turnip | — | Mar 10–Mar 24 | 254 | two-plantings: Plant Mar 10 and again by Sep 16; both mature before Nov 19. | Sep 16 |
| Kohlrabi | — | Feb 24–Mar 10 | 268 | two-plantings: Plant Feb 24 and again by Sep 11; both mature before Nov 19. | Sep 11 |
| Bok Choy | Mar 10 | Mar 31–Apr 7 | 219 | two-plantings: Plant Mar 31 and again by Sep 7; both mature before Nov 5. | Sep 7 |
| Collards | Jan 27 | Mar 10–Mar 24 | 254 | two-plantings: Plant Mar 10 and again by Sep 6; both mature before Nov 19. | Sep 6 |
| Cantaloupe | Mar 24 | Apr 21–Apr 28 | 163 | fits: 85 days to maturity, 163 available after Apr 21. | Jun 24 |
| Chives | Jan 13 | Apr 14–Apr 21 | 219 | fits: 90 days to maturity, 219 available after Apr 14. | — |
| Dill | — | Feb 10–May 5 | 268 | two-plantings: Plant Feb 10 and again by Aug 28; both mature before Nov 5. | Aug 28 |
| Oregano | Jan 27 | Apr 14–Apr 21 | 219 | fits: 80 days to maturity, 219 available after Apr 14. | — |
| Rosemary | Jan 13 | Apr 14–Apr 21 | 205 | fits: 80 days to maturity, 205 available after Apr 14. | — |
| Sage | Feb 10 | Apr 14–Apr 21 | 219 | fits: 75 days to maturity, 219 available after Apr 14. | — |
| Thyme | Jan 27 | Apr 14–Apr 21 | 219 | fits: 90 days to maturity, 219 available after Apr 14. | — |
| Calendula | Feb 24 | Mar 24–Apr 7 | 226 | two-plantings: Plant Mar 24 and again by Sep 2; both mature before Nov 5. | Sep 2 |
| Cosmos | Mar 10 | Apr 7–Apr 21 | 191 | two-plantings: Plant Apr 7 and again by Aug 2; both mature before Oct 15. | Aug 2 |
| Lavender | Jan 13 | Apr 7–Apr 21 | 226 | fits: 90 days to maturity, 226 available after Apr 7. | — |
| Marigolds | Feb 24 | Apr 7–Apr 14 | 191 | two-plantings: Plant Apr 7 and again by Aug 12; both mature before Oct 15. | Aug 12 |
| Melons | Mar 24 | Apr 21–Apr 28 | 163 | fits: 85 days to maturity, 163 available after Apr 21. | Jun 24 |
| Mint | — | Apr 7–Apr 21 | 226 | fits: 90 days to maturity, 226 available after Apr 7. | — |
| Nasturtiums | Mar 10 | Apr 7–Apr 14 | 191 | two-plantings: Plant Apr 7 and again by Aug 7; both mature before Oct 15. | Aug 7 |
| Pole Beans | — | Apr 14–Apr 28 | 184 | fits: 65 days to maturity, 184 available after Apr 14. | Jul 28 |
| Spaghetti Squash | Mar 24 | Apr 21–Apr 28 | 170 | fits: 90 days to maturity, 170 available after Apr 21. | Jun 26 |
| Sunflowers | — | Apr 7–Apr 21 | 191 | fits: 70 days to maturity, 191 available after Apr 7. | Jul 23 |
| Tomatillos | Feb 10 | Apr 14–Apr 21 | 170 | fits: 75 days to maturity, 170 available after Apr 14. | Jul 4 |
| Watermelon | Mar 24 | Apr 14–Apr 21 | 170 | fits: 80 days to maturity, 170 available after Apr 14. | Jun 29 |
| Yellow Squash | Mar 24 | Apr 21–Apr 28 | 177 | two-plantings: Plant Apr 21 and again by Aug 7; both mature before Oct 15. | Aug 7 |
| Zinnias | Mar 10 | Apr 7–Apr 21 | 191 | two-plantings: Plant Apr 7 and again by Aug 2; both mature before Oct 15. | Aug 2 |
Month by month in Alton
| Month | What to do |
|---|---|
| January | Start indoors: Chives (Jan 13), Lavender (Jan 13), Onion (Jan 13), Rosemary (Jan 13), Celery (Jan 27), Collards (Jan 27), +5 more. |
| February | Start indoors: Broccoli (Feb 10), Brussel Sprouts (Feb 10), Cabbage (Feb 10), Lettuce (Feb 10), Sage (Feb 10), Swiss Chard (Feb 10), +6 more. Direct sow from: Arugula (Feb 10), Beets (Feb 10), Dill (Feb 10), Peas (Feb 10), Radish (Feb 10), Spinach (Feb 10), +1 more. |
| March | Start indoors: Basil (Mar 3), Tomato (Mar 3), Bok Choy (Mar 10), Corn (Mar 10), Cosmos (Mar 10), Nasturtiums (Mar 10), +11 more. Direct sow from: Cilantro (Mar 10), Turnip (Mar 10), Carrots (Mar 17), Potatoes (Mar 24). Transplant from: Broccoli (Mar 10), Brussel Sprouts (Mar 10), Cabbage (Mar 10), Collards (Mar 10), Kale (Mar 10), Lettuce (Mar 10), +6 more. Plant: Strawberry (Mar 3). |
| April | Direct sow from: Sunflowers (Apr 7), Beans (Apr 14), Pole Beans (Apr 14). Transplant from: Cosmos (Apr 7), Lavender (Apr 7), Marigolds (Apr 7), Mint (Apr 7), Nasturtiums (Apr 7), Zinnias (Apr 7), +23 more. Last frost around April 7. |
| May | Frost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini. |
| June | Last sowing dates: Butternut Squash (Jun 16), Pumpkin (Jun 16), Cantaloupe (Jun 24), Celery (Jun 24), Melons (Jun 24), Spaghetti Squash (Jun 26), +2 more. |
| July | Last sowing dates: Pepper (Jul 4), Tomatillos (Jul 4), Eggplant (Jul 9), Corn (Jul 11), Sunflowers (Jul 23), Brussel Sprouts (Jul 28), +1 more. |
| August | Last sowing dates: Basil (Aug 2), Cosmos (Aug 2), Cucumber (Aug 2), Zinnias (Aug 2), Broccoli (Aug 3), Nasturtiums (Aug 7), +13 more. |
| September | Last sowing dates: Calendula (Sep 2), Cilantro (Sep 2), Collards (Sep 6), Scallions (Sep 6), Bok Choy (Sep 7), Lettuce (Sep 7), +6 more. |
| October | Direct sow from: Garlic (Oct 29). First frost around October 29. |
| November | Last sowing dates: Garlic (Nov 19). |
| 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 Alton, IL (ZIP 62002)?
The median last spring frost date for Alton, IL (ZIP code 62002) is around April 7. 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 March 27; one in ten it runs past April 19.
What is the first fall frost date in Alton, IL?
The median first fall frost date for Alton, IL is around October 29. 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 October 14 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Alton, IL?
The frost-free growing season in Alton is about 205 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 Alton (205 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 Alton, IL?
Alton, IL is in USDA hardiness zone 7a (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 Alton, IL?
Start tomatoes indoors Mar 3 and plant out Apr 21 in Alton. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Alton?
Two: plant Mar 10 and again by Sep 7; both mature before Nov 5.
When do I plant garlic in Alton?
Oct 29 to Nov 19; it overwinters and is ready the following summer.
Can I get two tomato crops in Alton?
Yes: plant out Apr 21 for a summer crop, and set out a second round of transplants by Jun 29 for a fall crop.
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