Frost Dates for Bethlehem, PA
In Bethlehem, PA, the average last spring frost is around Apr 20 and the average first fall frost around Oct 24, for a growing season of about 184 days. For frost-tender plants, wait until May 6, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Allentown Intl. Airport, PA weather station, 5 miles away, elevation 390 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 6 | Oct 8 |
| 20% | Apr 30 | Oct 13 |
| 30% | Apr 26 | Oct 17 |
| 40% | Apr 23 | Oct 21 |
| 50% | Apr 20 | Oct 24 |
| 60% | Apr 17 | Oct 27 |
| 70% | Apr 14 | Oct 31 |
| 80% | Apr 11 | Nov 2 |
| 90% | Apr 6 | Nov 6 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 2 | Oct 12 |
| Frost / freeze (32°F) | Apr 20 | Oct 24 |
| Hard freeze (28°F) | Apr 5 | Nov 4 |
Planting calendar for Bethlehem
Transplant Apr 27 – May 11
Transplant May 4 – May 18
Transplant May 4 – May 18
Transplant Apr 27 – May 11
Sow or transplant Apr 27 – May 11
Sow or transplant Apr 27 – May 11
Sow or transplant May 4 – May 18
Sow or transplant Mar 23 – Apr 6
Fall sowing Aug 29 – Sep 26
Fall sowing Aug 29 – Sep 19
Fall sowing Aug 15 – Aug 29
Sow or transplant Mar 23 – Apr 6
Fall sowing Aug 15 – Sep 12
Transplant Apr 6 – Apr 20
Fall sowing Aug 1 – Aug 15
Transplant Mar 30 – Apr 13
Fall sowing Aug 1 – Aug 15
Fall sowing Aug 1 – Aug 15
Fall sowing Sep 12 – Oct 3
Fall sowing Aug 15 – Aug 29
Plant Mar 23 – Apr 6
Based on the average last frost (Apr 20) and first frost (Oct 24). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.