What is the best time of year to sealcoat in Pennsylvania?
Short answer
Late spring through early fall. Sealcoat needs the pavement above about 50°F day and night through the whole cure, and a dry forecast for 24 hours after it goes down. In Delaware and Chester County that window runs to roughly the end of October.
Answered by Sean McCullough, owner of FGG Sealcoating · Serving Delaware County, Pennsylvania and Chester County, Pennsylvania
What sealcoat needs to cure
Two things: warmth and dry weather, both lasting through the whole cure.
- Warmth. The pavement surface has to stay above about 50°F, day and night. Below that the coat cures slowly or not properly at all.
- Dry weather. Rain within 24 hours of application can wash a fresh coat away or damage it before it sets.
The part people miss is the night. A mild afternoon in late October can be followed by a night near freezing, and the coat is still curing then. The number that decides the day is the overnight low, not the high.
What that means in Pennsylvania
In Delaware and Chester County, reliably warm days and nights arrive in late spring and hold into early fall. The window closes around the end of October, when the nights stop cooperating. Inside that window, the question for any given day is the forecast: warm enough overnight, and dry for the 24 hours after.
The window is closing now. Driveways sealed in the next few weeks still go down this year; after that, sealcoating waits for spring.
What happens in winter instead
Sealcoating stops. Driveway work does not. Hot-applied rubberized crack filling and pothole patching do not need 50°F, and winter is when an open crack does the most harm: water sits in it, freezes, expands, and widens it from the inside. Filling cracks before or during the freeze means the driveway is ready to seal as soon as spring arrives.
Related questions
How cold is too cold to sealcoat?
Below about 50°F at the surface, at any point in the cure — including overnight. A warm afternoon followed by a cold night is not good enough, because the coat is still curing through the night.
Is air temperature or pavement temperature what matters?
Pavement temperature. Asphalt holds and loses heat differently from the air above it, so a forecast high is only a rough guide to what the surface is actually doing.
What does rain do to a fresh sealcoat?
Rain within the first 24 hours can wash a fresh coat off or leave it damaged before it has cured. That makes the forecast as important as the thermometer when picking a day.
Can anything be done to a driveway in winter?
Yes. Hot-applied rubberized crack filling and pothole patching do not need 50°F and run through the winter. Filling cracks before the freeze keeps water out of the base, which is when it does the most damage.