Frost dates for 18101 — Allentown, PA
Last spring frostApr 20median date
First fall frostOct 24median date
Growing season187 daysfrost-free
Hardiness zone7aZone 7a
How Allentown compares
- In 8 years out of 10, the last spring frost in Allentown falls between April 6 and May 6, a 30-day window. The first fall frost falls between October 8 and November 6.
- The median last frost is 7 days earlier than the Pennsylvania median of Apr 27.
- Its 187-day growing season is longer than 73% of the 1,787 Pennsylvania places with a regular frost season (state median 175 days).
- The last frost is 4 days later than the zone 7a median of Apr 16. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 7a chart.
- The weather station records an average of 118 nights a year at or below 32°F.
- Compared with Philadelphia, PA, 73 km away, the last frost here is 21 days later than there and the growing season is 45 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 6 |
| 50% (median) | April 20 |
| 10% (safe for tender plants) | May 6 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 8 |
| 50% (median) | October 24 |
| 90% (late) | November 6 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Allentown, PA
Frost dates for 18101 — Allentown, PA — last frost Apr 20, first frost Oct 24, zone 7a. whenisthelastfrost.com
Crop
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Start indoors: Jan 26 to Feb 9Transplant outside: Mar 23 to Apr 6
Start indoors: Feb 9 to Feb 23Transplant outside: May 4 to May 18
Start indoors: Feb 9 to Feb 23Transplant outside: May 4 to May 18
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 27 to May 11
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 30 to Apr 13Sow outdoors: Mar 23 to Apr 27Plant for fall: Aug 29 to Sep 26
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 23 to Apr 6Sow outdoors: Mar 23 to Apr 6Plant for fall: Aug 15 to Sep 5
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 6 to Apr 20Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 30 to Apr 13Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 6 to Apr 20Plant for fall: Jul 18 to Aug 8
Start indoors: Mar 9 to Mar 23Transplant outside: May 11 to May 25Sow outdoors: May 11 to May 25
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 27 to May 11
Sow outdoors: Mar 9 to Mar 30Plant for fall: Aug 1 to Aug 22
Sow outdoors: Mar 9 to Mar 30Plant for fall: Aug 29 to Sep 19
Sow outdoors: Mar 16 to Apr 27Plant for fall: Sep 12 to Oct 3
Start indoors: Mar 23 to Mar 30Transplant outside: May 4 to May 11Sow outdoors: Apr 27 to May 11Plant for fall: Aug 8 to Aug 22
Start indoors: Mar 23 to Mar 30Sow outdoors: Apr 27 to May 11Plant for fall: Aug 15 to Aug 29
Start indoors: Mar 23 to Mar 30Sow outdoors: Apr 27 to May 11
Start indoors: Mar 23 to Mar 30Transplant outside: May 4 to May 18
Sow outdoors: Mar 30 to Apr 27Plant for fall: Aug 1 to Aug 15
Sow outdoors: Mar 30 to Apr 27Plant for fall: Aug 15 to Aug 29
Sow outdoors: Mar 30 to Apr 20
Sow outdoors: Apr 6 to May 4Plant for fall: Aug 15 to Aug 29
Sow outdoors: Apr 6 to Apr 27Plant for fall: Aug 29 to Sep 19
Sow outdoors: Apr 27 to May 18Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 27 to May 11
Transplant outside: May 4 to May 25
Plant for fall: Oct 10 to Nov 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Allentown, PA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 26 – Feb 9 | Mar 23 – Apr 6 | — | — |
| Peppers | Feb 9 – Feb 23 | May 4 – May 18 | — | — |
| Eggplant | Feb 9 – Feb 23 | May 4 – May 18 | — | — |
| Tomatoes | Feb 23 – Mar 9 | Apr 27 – May 11 | — | — |
| Lettuce | Feb 23 – Mar 9 | Mar 30 – Apr 13 | Mar 23 – Apr 27 | Aug 29 – Sep 26 |
| Kale | Feb 23 – Mar 9 | Mar 23 – Apr 6 | Mar 23 – Apr 6 | Aug 15 – Sep 5 |
| Broccoli | Feb 23 – Mar 9 | Apr 6 – Apr 20 | — | Jul 18 – Aug 8 |
| Cabbage | Feb 23 – Mar 9 | Mar 30 – Apr 13 | — | Jul 18 – Aug 8 |
| Cauliflower | Feb 23 – Mar 9 | Apr 6 – Apr 20 | — | Jul 18 – Aug 8 |
| Okra | Mar 9 – Mar 23 | May 11 – May 25 | May 11 – May 25 | — |
| Basil | Mar 9 – Mar 23 | Apr 27 – May 11 | — | — |
| Peas | — | — | Mar 9 – Mar 30 | Aug 1 – Aug 22 |
| Spinach | — | — | Mar 9 – Mar 30 | Aug 29 – Sep 19 |
| Radishes | — | — | Mar 16 – Apr 27 | Sep 12 – Oct 3 |
| Cucumbers | Mar 23 – Mar 30 | May 4 – May 11 | Apr 27 – May 11 | Aug 8 – Aug 22 |
| Zucchini & Summer Squash | Mar 23 – Mar 30 | — | Apr 27 – May 11 | Aug 15 – Aug 29 |
| Winter Squash & Pumpkins | Mar 23 – Mar 30 | — | Apr 27 – May 11 | — |
| Melons & Watermelon | Mar 23 – Mar 30 | May 4 – May 18 | — | — |
| Carrots | — | — | Mar 30 – Apr 27 | Aug 1 – Aug 15 |
| Beets | — | — | Mar 30 – Apr 27 | Aug 15 – Aug 29 |
| Potatoes | — | — | Mar 30 – Apr 20 | — |
| Swiss Chard | — | — | Apr 6 – May 4 | Aug 15 – Aug 29 |
| Cilantro | — | — | Apr 6 – Apr 27 | Aug 29 – Sep 19 |
| Green Beans | — | — | Apr 27 – May 18 | Aug 8 – Aug 22 |
| Sweet Corn | — | — | Apr 27 – May 11 | — |
| Sweet Potatoes | — | May 4 – May 25 | — | — |
| Garlic | — | — | — | Oct 10 – Nov 14 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Allentown Intl Ap, PA weather station, 6 km away (elevation 390 ft (119 m)).
ZIP codes in Allentown: 18101 18102 18103 18104 18105 18106 18109 18195
Frost dates near Allentown
- Catasauqua Apr 20 · Oct 24
- Whitehall Apr 20 · Oct 24
- Coplay Apr 20 · Oct 24
- Emmaus Apr 20 · Oct 24
- Center Valley Apr 20 · Oct 24
- Bethlehem Apr 20 · Oct 24
- Lehigh Valley Apr 20 · Oct 24
- East Texas Apr 26 · Oct 14
Frequently asked questions
When is the last frost in Allentown, PA?
The median last spring frost in Allentown, PA is April 20. There is still about a 10% chance of frost after May 6, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Allentown, PA?
The median first fall frost is October 24, with about a 10% chance of frost before October 8.
How long is the growing season in Allentown, PA?
About 187 days between the median last spring frost and first fall frost.
What planting zone is Allentown, PA?
Allentown, PA is in USDA hardiness zone 7a.