Frost Dates for Janesville, WI 53546
Last spring frost May 6 · First fall frost October 4 · 151 frost-free days · USDA Zone 5b
ZIP 53546 has about 29,900 people, the largest of 3 ZIP codes in Janesville.
Moderate season: 151 frost-free days. Spring frost risk spans April 21–May 21 (30 days). Fall frost risk spans September 21–October 17 (26 days).
Frost probability for 53546
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | May 21 | May 6 | April 21 |
| Fall (first frost) | September 21 | October 4 | October 17 |
Dates come from NOAA 1971–2000 freeze probabilities at FT ATKINSON WWTP (29.1 km away); the 50% date is the median year.
Frost dates by ZIP code in Janesville, WI
| ZIP | Last spring frost (50%) | First fall frost (50%) | Zone |
|---|---|---|---|
| 53546 | May 6 | October 4 | 5b |
| 53545 | May 2 | October 3 | 5b |
| 53548 | May 2 | October 2 | 5b |
Which crops fit a 151-day season in Janesville
In Janesville (151 frost-free days, a moderate season), 34 of 56 planner crops fit outright, 21 get two plantings, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Apr 1 | May 20–May 27 | 109 | fits: 80 days to maturity, 109 available after May 20. | Jun 4 |
| Pepper | Mar 25 | May 20–May 27 | 109 | fits: 75 days to maturity, 109 available after May 20. | Jun 9 |
| Lettuce | Mar 11 | Apr 8–Apr 15 | 186 | two-plantings: Plant Apr 8 and again by Aug 13; both mature before Oct 11. | Aug 13 |
| Carrots | — | Apr 15–Apr 22 | 193 | fits: 70 days to maturity, 193 available after Apr 15. | Aug 2 |
| Cucumber | Apr 15 | May 20–May 27 | 123 | fits: 60 days to maturity, 123 available after May 20. | Jul 8 |
| Beans | — | May 13–May 27 | 137 | two-plantings: Plant May 13 and again by Jul 15; both mature before Sep 27. | Jul 15 |
| Peas | — | Mar 11–May 20 | 214 | fits: 65 days to maturity, 214 available after Mar 11. | Jul 24 |
| Zucchini | Apr 22 | May 20–May 27 | 123 | fits: 55 days to maturity, 123 available after May 20. | Jul 13 |
| Onion | Feb 11 | Apr 8–Apr 22 | 186 | fits: 100 days to maturity, 186 available after Apr 8. | — |
| Spinach | — | Mar 11–Apr 29 | 228 | two-plantings: Plant Mar 11 and again by Sep 1; both mature before Oct 25. | Sep 1 |
| Kale | Feb 25 | Apr 8–Apr 22 | 200 | two-plantings: Plant Apr 8 and again by Aug 17; both mature before Oct 25. | Aug 17 |
| Broccoli | Mar 11 | Apr 8–Apr 22 | 186 | fits: 80 days to maturity, 186 available after Apr 8. | Jul 9 |
| Cabbage | Mar 11 | Apr 8–Apr 22 | 200 | fits: 70 days to maturity, 200 available after Apr 8. | Aug 2 |
| Radish | — | Mar 11–Jun 3 | 214 | two-plantings: Plant Mar 11 and again by Sep 2; both mature before Oct 11. | Sep 2 |
| Beets | — | Mar 11–Jun 3 | 214 | two-plantings: Plant Mar 11 and again by Aug 3; both mature before Oct 11. | Aug 3 |
| Potatoes | — | Apr 22–Apr 29 | 172 | fits: 90 days to maturity, 172 available after Apr 22. | — |
| Garlic | — | Oct 4 | 256 | overwinter: Plant Oct 4 to Oct 25; harvest the following summer. | Oct 25 |
| Strawberry | — | Apr 1–May 27 | 207 | perennial: A perennial: plant Apr 1; it fruits from the following year and keeps producing for several years. | — |
| Corn | Apr 8 | May 13–May 20 | 123 | fits: 75 days to maturity, 123 available after May 13. | Jun 16 |
| Pumpkin | Apr 22 | May 20–May 20 | 116 | fits: 100 days to maturity, 116 available after May 20. | May 22 |
| Cauliflower | Mar 25 | Apr 29–May 13 | 165 | fits: 75 days to maturity, 165 available after Apr 29. | Jul 14 |
| Swiss Chard | Mar 11 | Apr 22–Apr 22 | 172 | two-plantings: Plant Apr 22 and again by Aug 3; both mature before Oct 11. | Aug 3 |
| Arugula | — | Mar 11–Jun 3 | 228 | two-plantings: Plant Mar 11 and again by Sep 1; both mature before Oct 25. | Sep 1 |
| Brussel Sprouts | Mar 11 | Apr 8–Apr 22 | 200 | fits: 100 days to maturity, 200 available after Apr 8. | Jul 3 |
| Butternut Squash | Apr 22 | May 20–May 27 | 116 | fits: 100 days to maturity, 116 available after May 20. | May 22 |
| Eggplant | Mar 18 | May 20–May 27 | 109 | fits: 70 days to maturity, 109 available after May 20. | Jun 14 |
| Okra | Apr 8 | May 13–May 20 | 130 | two-plantings: Plant May 13 and again by Jul 13; both mature before Sep 20. | Jul 13 |
| Basil | Apr 1 | May 27–May 27 | 116 | fits: 60 days to maturity, 116 available after May 27. | Jul 8 |
| Cilantro | — | Apr 8–Apr 29 | 186 | two-plantings: Plant Apr 8 and again by Aug 8; both mature before Oct 11. | Aug 8 |
| Parsley | Feb 25 | May 13–May 20 | 151 | fits: 70 days to maturity, 151 available after May 13. | Jul 19 |
| Celery | Feb 25 | May 13–May 27 | 151 | fits: 120 days to maturity, 151 available after May 13. | May 30 |
| Scallions | Feb 25 | Apr 8–Apr 22 | 200 | two-plantings: Plant Apr 8 and again by Aug 12; both mature before Oct 25. | Aug 12 |
| Turnip | — | Apr 8–Apr 22 | 200 | two-plantings: Plant Apr 8 and again by Aug 22; both mature before Oct 25. | Aug 22 |
| Kohlrabi | — | Mar 25–Apr 8 | 214 | two-plantings: Plant Mar 25 and again by Aug 17; both mature before Oct 25. | Aug 17 |
| Bok Choy | Apr 8 | Apr 29–May 6 | 165 | two-plantings: Plant Apr 29 and again by Aug 13; both mature before Oct 11. | Aug 13 |
| Collards | Feb 25 | Apr 8–Apr 22 | 200 | two-plantings: Plant Apr 8 and again by Aug 12; both mature before Oct 25. | Aug 12 |
| Cantaloupe | Apr 22 | May 20–May 27 | 109 | fits: 85 days to maturity, 109 available after May 20. | May 30 |
| Chives | Feb 11 | May 13–May 20 | 165 | fits: 90 days to maturity, 165 available after May 13. | — |
| Dill | — | Mar 11–Jun 3 | 214 | two-plantings: Plant Mar 11 and again by Aug 3; both mature before Oct 11. | Aug 3 |
| Oregano | Feb 25 | May 13–May 20 | 165 | fits: 80 days to maturity, 165 available after May 13. | — |
| Rosemary | Feb 11 | May 13–May 20 | 151 | fits: 80 days to maturity, 151 available after May 13. | — |
| Sage | Mar 11 | May 13–May 20 | 165 | fits: 75 days to maturity, 165 available after May 13. | — |
| Thyme | Feb 25 | May 13–May 20 | 165 | fits: 90 days to maturity, 165 available after May 13. | — |
| Calendula | Mar 25 | Apr 22–May 6 | 172 | two-plantings: Plant Apr 22 and again by Aug 8; both mature before Oct 11. | Aug 8 |
| Cosmos | Apr 8 | May 6–May 20 | 137 | two-plantings: Plant May 6 and again by Jul 8; both mature before Sep 20. | Jul 8 |
| Lavender | Feb 11 | May 6–May 20 | 172 | fits: 90 days to maturity, 172 available after May 6. | — |
| Marigolds | Mar 25 | May 6–May 13 | 137 | two-plantings: Plant May 6 and again by Jul 18; both mature before Sep 20. | Jul 18 |
| Melons | Apr 22 | May 20–May 27 | 109 | fits: 85 days to maturity, 109 available after May 20. | May 30 |
| Mint | — | May 6–May 20 | 172 | fits: 90 days to maturity, 172 available after May 6. | — |
| Nasturtiums | Apr 8 | May 6–May 13 | 137 | two-plantings: Plant May 6 and again by Jul 13; both mature before Sep 20. | Jul 13 |
| Pole Beans | — | May 13–May 27 | 130 | fits: 65 days to maturity, 130 available after May 13. | Jul 3 |
| Spaghetti Squash | Apr 22 | May 20–May 27 | 116 | fits: 90 days to maturity, 116 available after May 20. | Jun 1 |
| Sunflowers | — | May 6–May 20 | 137 | fits: 70 days to maturity, 137 available after May 6. | Jun 28 |
| Tomatillos | Mar 11 | May 13–May 20 | 116 | fits: 75 days to maturity, 116 available after May 13. | Jun 9 |
| Watermelon | Apr 22 | May 13–May 20 | 116 | fits: 80 days to maturity, 116 available after May 13. | Jun 4 |
| Yellow Squash | Apr 22 | May 20–May 27 | 123 | fits: 55 days to maturity, 123 available after May 20. | Jul 13 |
| Zinnias | Apr 8 | May 6–May 20 | 137 | two-plantings: Plant May 6 and again by Jul 8; both mature before Sep 20. | Jul 8 |
Month by month in Janesville
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start indoors: Chives (Feb 11), Lavender (Feb 11), Onion (Feb 11), Rosemary (Feb 11), Celery (Feb 25), Collards (Feb 25), +5 more. |
| March | Start indoors: Broccoli (Mar 11), Brussel Sprouts (Mar 11), Cabbage (Mar 11), Lettuce (Mar 11), Sage (Mar 11), Swiss Chard (Mar 11), +6 more. Direct sow from: Arugula (Mar 11), Beets (Mar 11), Dill (Mar 11), Peas (Mar 11), Radish (Mar 11), Spinach (Mar 11), +1 more. |
| April | Start indoors: Basil (Apr 1), Tomato (Apr 1), Bok Choy (Apr 8), Corn (Apr 8), Cosmos (Apr 8), Nasturtiums (Apr 8), +11 more. Direct sow from: Cilantro (Apr 8), Turnip (Apr 8), Carrots (Apr 15), Potatoes (Apr 22). Transplant from: Broccoli (Apr 8), Brussel Sprouts (Apr 8), Cabbage (Apr 8), Collards (Apr 8), Kale (Apr 8), Lettuce (Apr 8), +6 more. Plant: Strawberry (Apr 1). |
| May | Direct sow from: Sunflowers (May 6), Beans (May 13), Pole Beans (May 13). Transplant from: Cosmos (May 6), Lavender (May 6), Marigolds (May 6), Mint (May 6), Nasturtiums (May 6), Zinnias (May 6), +23 more. Last frost around May 6. Last sowing dates: Butternut Squash (May 22), Pumpkin (May 22), Cantaloupe (May 30), Celery (May 30), Melons (May 30). |
| June | Last sowing dates: Spaghetti Squash (Jun 1), Tomato (Jun 4), Watermelon (Jun 4), Pepper (Jun 9), Tomatillos (Jun 9), Eggplant (Jun 14), +2 more. |
| July | Last sowing dates: Brussel Sprouts (Jul 3), Pole Beans (Jul 3), Basil (Jul 8), Cosmos (Jul 8), Cucumber (Jul 8), Zinnias (Jul 8), +10 more. |
| August | Last sowing dates: Cabbage (Aug 2), Carrots (Aug 2), Beets (Aug 3), Dill (Aug 3), Swiss Chard (Aug 3), Calendula (Aug 8), +8 more. |
| September | Last sowing dates: Arugula (Sep 1), Spinach (Sep 1), Radish (Sep 2). |
| October | Direct sow from: Garlic (Oct 4). First frost around October 4. Last sowing dates: Garlic (Oct 25). |
| November | Harvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year. |
| 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 Janesville, WI (ZIP 53546)?
The median last spring frost date for Janesville, WI (ZIP code 53546) is around May 6. 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 21; one in ten it runs past May 21.
What is the first fall frost date in Janesville, WI?
The median first fall frost date for Janesville, WI is around October 4. 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 21 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Janesville, WI?
The frost-free growing season in Janesville is about 151 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 Janesville (151 frost-free days, a moderate season), 34 of 56 planner crops fit outright, 21 get two plantings, 1 crop is perennial.
What USDA hardiness zone is Janesville, WI?
Janesville, WI is in USDA hardiness zone 5b (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 Janesville, WI?
Start tomatoes indoors Apr 1 and plant out May 20 in Janesville. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Janesville?
Two: plant Apr 8 and again by Aug 13; both mature before Oct 11.
When do I plant garlic in Janesville?
Oct 4 to Oct 25; it overwinters and is ready the following summer.
Which nearby ZIP has a longer season?
Beloit (ZIP 53511) has 159 frost-free days, 8 more than Janesville (ZIP 53546). See Beloit ZIP 53511 frost dates
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