Allentown, PA Frost Dates
Average frost dates, USDA hardiness zone, and growing season length for Allentown, Pennsylvania.
Gardening in Allentown
The Lehigh Valley's largest city has fertile limestone soil and a growing food culture powered by the region's diverse communities.
Zone 6b with 191 frost-free days. The Lehigh Valley's limestone-derived soil is naturally fertile and slightly alkaline. The valley between Blue Mountain and South Mountain provides shelter.
The Allentown Fairgrounds Farmers Market is the Lehigh Valley's gathering place. The surrounding Pennsylvania Dutch country's agricultural expertise filters into the city.
What This Means for Allentown Gardeners
The average last spring frost in Allentown is around April 12, and the average first fall frost arrives around October 20. That gives you approximately 191 frost-free days to work with.
A solid, workable season. Most standard vegetable varieties have enough time to mature, though the longest-season crops (like sweet potatoes at 90+ days or large watermelons at 85+ days) need to be started early and chosen carefully. Indoor seed starting isn't optional — it's how you buy the extra weeks that make the difference between a good harvest and a great one.
These dates are based on NOAA 30-year Climate Normal data for the Allentown area. Your actual frost dates could shift 2-3 weeks in either direction in any given year. Learn more about our data sources.
What to Grow in Allentown
Allentown's 191-day season gives you plenty of time for most vegetables with good planning. Start warm-season crops indoors to maximize your window. Cool-season crops thrive in your spring and fall shoulder seasons. Recommended starting points: tomatoes, peppers, lettuce, carrots, beans, broccoli, garlic, and basil.
See the full Pennsylvania planting guide for all 40 plants: Pennsylvania Planting Calendar. Or enter your zip code for exact planting dates personalized to Allentown.
More About Zone 6B
Allentown is in USDA Hardiness Zone 6B, which means average annual extreme minimum temperatures between -5°F to 0°F. View the full Zone 6B planting guide.
See the complete planting calendar for Pennsylvania: Pennsylvania Planting Calendar.
Other Cities in Pennsylvania
Frequently Asked Questions
These dates are based on NOAA's 30-year Climate Normal data for the Allentown area. They represent historical averages, not predictions. In any given year, the actual last frost could be 2-3 weeks earlier or later. Microclimates within Allentown (urban heat islands, hilltops, low-lying valleys) can also shift your local frost dates by a week or more.
Start warm-season seeds indoors 6-8 weeks before your last frost (April 12) to maximize your 191-day window. Direct sow cold-hardy crops like peas and lettuce 3-4 weeks before last frost. Every week of early indoor starting matters at this season length. Enter your zip code for exact dates.