Frost Dates for Irwin, PA 15642
Last spring frost May 1 · First fall frost October 14 · 166 frost-free days · USDA Zone 6b
ZIP 15642 has about 46,300 people.
Moderate season: 166 frost-free days. Spring frost risk spans April 17–May 16 (29 days). Fall frost risk spans September 25–November 2 (38 days).
Frost probability for 15642
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | May 16 | May 1 | April 17 |
| Fall (first frost) | September 25 | October 14 | November 2 |
Dates come from NOAA 1971–2000 freeze probabilities at MCKEESPORT (12.0 km away); the 50% date is the median year.
Which crops fit a 166-day season in Irwin
In Irwin (166 frost-free days, a moderate season), 31 of 56 planner crops fit outright, 24 get two plantings, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Mar 27 | May 15–May 22 | 124 | fits: 80 days to maturity, 124 available after May 15. | Jun 14 |
| Pepper | Mar 20 | May 15–May 22 | 124 | fits: 75 days to maturity, 124 available after May 15. | Jun 19 |
| Lettuce | Mar 6 | Apr 3–Apr 10 | 201 | two-plantings: Plant Apr 3 and again by Aug 23; both mature before Oct 21. | Aug 23 |
| Carrots | — | Apr 10–Apr 17 | 208 | fits: 70 days to maturity, 208 available after Apr 10. | Aug 12 |
| Cucumber | Apr 10 | May 15–May 22 | 138 | two-plantings: Plant May 15 and again by Jul 18; both mature before Sep 30. | Jul 18 |
| Beans | — | May 8–May 22 | 152 | two-plantings: Plant May 8 and again by Jul 25; both mature before Oct 7. | Jul 25 |
| Peas | — | Mar 6–May 15 | 229 | fits: 65 days to maturity, 229 available after Mar 6. | Aug 3 |
| Zucchini | Apr 17 | May 15–May 22 | 138 | two-plantings: Plant May 15 and again by Jul 23; both mature before Sep 30. | Jul 23 |
| Onion | Feb 6 | Apr 3–Apr 17 | 201 | fits: 100 days to maturity, 201 available after Apr 3. | — |
| Spinach | — | Mar 6–Apr 24 | 243 | two-plantings: Plant Mar 6 and again by Sep 11; both mature before Nov 4. | Sep 11 |
| Kale | Feb 20 | Apr 3–Apr 17 | 215 | two-plantings: Plant Apr 3 and again by Aug 27; both mature before Nov 4. | Aug 27 |
| Broccoli | Mar 6 | Apr 3–Apr 17 | 201 | fits: 80 days to maturity, 201 available after Apr 3. | Jul 19 |
| Cabbage | Mar 6 | Apr 3–Apr 17 | 215 | fits: 70 days to maturity, 215 available after Apr 3. | Aug 12 |
| Radish | — | Mar 6–May 29 | 229 | two-plantings: Plant Mar 6 and again by Sep 12; both mature before Oct 21. | Sep 12 |
| Beets | — | Mar 6–May 29 | 229 | two-plantings: Plant Mar 6 and again by Aug 13; both mature before Oct 21. | Aug 13 |
| Potatoes | — | Apr 17–Apr 24 | 187 | fits: 90 days to maturity, 187 available after Apr 17. | — |
| Garlic | — | Oct 14 | 271 | overwinter: Plant Oct 14 to Nov 4; harvest the following summer. | Nov 4 |
| Strawberry | — | Mar 27–May 22 | 222 | perennial: A perennial: plant Mar 27; it fruits from the following year and keeps producing for several years. | — |
| Corn | Apr 3 | May 8–May 15 | 138 | fits: 75 days to maturity, 138 available after May 8. | Jun 26 |
| Pumpkin | Apr 17 | May 15–May 15 | 131 | fits: 100 days to maturity, 131 available after May 15. | Jun 1 |
| Cauliflower | Mar 20 | Apr 24–May 8 | 180 | fits: 75 days to maturity, 180 available after Apr 24. | Jul 24 |
| Swiss Chard | Mar 6 | Apr 17–Apr 17 | 187 | two-plantings: Plant Apr 17 and again by Aug 13; both mature before Oct 21. | Aug 13 |
| Arugula | — | Mar 6–May 29 | 243 | two-plantings: Plant Mar 6 and again by Sep 11; both mature before Nov 4. | Sep 11 |
| Brussel Sprouts | Mar 6 | Apr 3–Apr 17 | 215 | fits: 100 days to maturity, 215 available after Apr 3. | Jul 13 |
| Butternut Squash | Apr 17 | May 15–May 22 | 131 | fits: 100 days to maturity, 131 available after May 15. | Jun 1 |
| Eggplant | Mar 13 | May 15–May 22 | 124 | fits: 70 days to maturity, 124 available after May 15. | Jun 24 |
| Okra | Apr 3 | May 8–May 15 | 145 | two-plantings: Plant May 8 and again by Jul 23; both mature before Sep 30. | Jul 23 |
| Basil | Mar 27 | May 22–May 22 | 131 | fits: 60 days to maturity, 131 available after May 22. | Jul 18 |
| Cilantro | — | Apr 3–Apr 24 | 201 | two-plantings: Plant Apr 3 and again by Aug 18; both mature before Oct 21. | Aug 18 |
| Parsley | Feb 20 | May 8–May 15 | 166 | fits: 70 days to maturity, 166 available after May 8. | Jul 29 |
| Celery | Feb 20 | May 8–May 22 | 166 | fits: 120 days to maturity, 166 available after May 8. | Jun 9 |
| Scallions | Feb 20 | Apr 3–Apr 17 | 215 | two-plantings: Plant Apr 3 and again by Aug 22; both mature before Nov 4. | Aug 22 |
| Turnip | — | Apr 3–Apr 17 | 215 | two-plantings: Plant Apr 3 and again by Sep 1; both mature before Nov 4. | Sep 1 |
| Kohlrabi | — | Mar 20–Apr 3 | 229 | two-plantings: Plant Mar 20 and again by Aug 27; both mature before Nov 4. | Aug 27 |
| Bok Choy | Apr 3 | Apr 24–May 1 | 180 | two-plantings: Plant Apr 24 and again by Aug 23; both mature before Oct 21. | Aug 23 |
| Collards | Feb 20 | Apr 3–Apr 17 | 215 | two-plantings: Plant Apr 3 and again by Aug 22; both mature before Nov 4. | Aug 22 |
| Cantaloupe | Apr 17 | May 15–May 22 | 124 | fits: 85 days to maturity, 124 available after May 15. | Jun 9 |
| Chives | Feb 6 | May 8–May 15 | 180 | fits: 90 days to maturity, 180 available after May 8. | — |
| Dill | — | Mar 6–May 29 | 229 | two-plantings: Plant Mar 6 and again by Aug 13; both mature before Oct 21. | Aug 13 |
| Oregano | Feb 20 | May 8–May 15 | 180 | fits: 80 days to maturity, 180 available after May 8. | — |
| Rosemary | Feb 6 | May 8–May 15 | 166 | fits: 80 days to maturity, 166 available after May 8. | — |
| Sage | Mar 6 | May 8–May 15 | 180 | fits: 75 days to maturity, 180 available after May 8. | — |
| Thyme | Feb 20 | May 8–May 15 | 180 | fits: 90 days to maturity, 180 available after May 8. | — |
| Calendula | Mar 20 | Apr 17–May 1 | 187 | two-plantings: Plant Apr 17 and again by Aug 18; both mature before Oct 21. | Aug 18 |
| Cosmos | Apr 3 | May 1–May 15 | 152 | two-plantings: Plant May 1 and again by Jul 18; both mature before Sep 30. | Jul 18 |
| Lavender | Feb 6 | May 1–May 15 | 187 | fits: 90 days to maturity, 187 available after May 1. | — |
| Marigolds | Mar 20 | May 1–May 8 | 152 | two-plantings: Plant May 1 and again by Jul 28; both mature before Sep 30. | Jul 28 |
| Melons | Apr 17 | May 15–May 22 | 124 | fits: 85 days to maturity, 124 available after May 15. | Jun 9 |
| Mint | — | May 1–May 15 | 187 | fits: 90 days to maturity, 187 available after May 1. | — |
| Nasturtiums | Apr 3 | May 1–May 8 | 152 | two-plantings: Plant May 1 and again by Jul 23; both mature before Sep 30. | Jul 23 |
| Pole Beans | — | May 8–May 22 | 145 | fits: 65 days to maturity, 145 available after May 8. | Jul 13 |
| Spaghetti Squash | Apr 17 | May 15–May 22 | 131 | fits: 90 days to maturity, 131 available after May 15. | Jun 11 |
| Sunflowers | — | May 1–May 15 | 152 | fits: 70 days to maturity, 152 available after May 1. | Jul 8 |
| Tomatillos | Mar 6 | May 8–May 15 | 131 | fits: 75 days to maturity, 131 available after May 8. | Jun 19 |
| Watermelon | Apr 17 | May 8–May 15 | 131 | fits: 80 days to maturity, 131 available after May 8. | Jun 14 |
| Yellow Squash | Apr 17 | May 15–May 22 | 138 | two-plantings: Plant May 15 and again by Jul 23; both mature before Sep 30. | Jul 23 |
| Zinnias | Apr 3 | May 1–May 15 | 152 | two-plantings: Plant May 1 and again by Jul 18; both mature before Sep 30. | Jul 18 |
Month by month in Irwin
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start indoors: Chives (Feb 6), Lavender (Feb 6), Onion (Feb 6), Rosemary (Feb 6), Celery (Feb 20), Collards (Feb 20), +5 more. |
| March | Start indoors: Broccoli (Mar 6), Brussel Sprouts (Mar 6), Cabbage (Mar 6), Lettuce (Mar 6), Sage (Mar 6), Swiss Chard (Mar 6), +8 more. Direct sow from: Arugula (Mar 6), Beets (Mar 6), Dill (Mar 6), Peas (Mar 6), Radish (Mar 6), Spinach (Mar 6), +1 more. Plant: Strawberry (Mar 27). |
| April | Start indoors: Bok Choy (Apr 3), Corn (Apr 3), Cosmos (Apr 3), Nasturtiums (Apr 3), Okra (Apr 3), Zinnias (Apr 3), +9 more. Direct sow from: Cilantro (Apr 3), Turnip (Apr 3), Carrots (Apr 10), Potatoes (Apr 17). Transplant from: Broccoli (Apr 3), Brussel Sprouts (Apr 3), Cabbage (Apr 3), Collards (Apr 3), Kale (Apr 3), Lettuce (Apr 3), +6 more. |
| May | Direct sow from: Sunflowers (May 1), Beans (May 8), Pole Beans (May 8). Transplant from: Cosmos (May 1), Lavender (May 1), Marigolds (May 1), Mint (May 1), Nasturtiums (May 1), Zinnias (May 1), +23 more. Last frost around May 1. |
| June | Last sowing dates: Butternut Squash (Jun 1), Pumpkin (Jun 1), Cantaloupe (Jun 9), Celery (Jun 9), Melons (Jun 9), Spaghetti Squash (Jun 11), +6 more. |
| July | Last sowing dates: Sunflowers (Jul 8), Brussel Sprouts (Jul 13), Pole Beans (Jul 13), Basil (Jul 18), Cosmos (Jul 18), Cucumber (Jul 18), +10 more. |
| August | Last sowing dates: Peas (Aug 3), Cabbage (Aug 12), Carrots (Aug 12), Beets (Aug 13), Dill (Aug 13), Swiss Chard (Aug 13), +8 more. |
| September | Last sowing dates: Turnip (Sep 1), Arugula (Sep 11), Spinach (Sep 11), Radish (Sep 12). |
| October | Direct sow from: Garlic (Oct 14). First frost around October 14. |
| November | Last sowing dates: Garlic (Nov 4). |
| 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 Irwin, PA (ZIP 15642)?
The median last spring frost date for Irwin, PA (ZIP code 15642) is around May 1. 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 17; one in ten it runs past May 16.
What is the first fall frost date in Irwin, PA?
The median first fall frost date for Irwin, PA is around October 14. 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 25 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Irwin, PA?
The frost-free growing season in Irwin is about 166 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 Irwin (166 frost-free days, a moderate season), 31 of 56 planner crops fit outright, 24 get two plantings, 1 crop is perennial.
What USDA hardiness zone is Irwin, PA?
Irwin, PA is in USDA hardiness zone 6b (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 Irwin, PA?
Start tomatoes indoors Mar 27 and plant out May 15 in Irwin. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Irwin?
Two: plant Apr 3 and again by Aug 23; both mature before Oct 21.
When do I plant garlic in Irwin?
Oct 14 to Nov 4; it overwinters and is ready the following summer.
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