In central North Carolina the sealing season is long, and the thing that ends a job early is more often a thunderstorm than the cold. Here is the temperature rule sealer works to, how the Raleigh calendar lines up against it month by month, and why spring and fall are the comfortable ends of the year.
Asphalt sealer is a water based emulsion. It cures as the water leaves it, and it needs warmth to do that. The usual manufacturer rule is air and pavement at 50F or above and climbing, with no rain expected for the next day, and no overnight drop toward freezing while it is still soft. Below that, the coat stays tacky, tracks onto shoes and tires, and can wash off in the next shower.
There is a top end as well. On the hottest summer afternoons the pavement can be so hot that sealer flashes dry on top before it has bonded underneath. That is why summer work starts early in the morning.
These come from NOAA's 1991 to 2020 climate normals for Raleigh-Durham International Airport, the official station for the area.
NOAA's state climate summary describes North Carolina summers as warm and moist, with frequent thunderstorms in the afternoons and evenings. Anyone who has watched a clear morning in Raleigh turn into a downpour by four o'clock knows what that means for a coat that needs dry hours.
Raleigh winters are mild by most standards. NOAA's normals give only about two days a year when the high stays at or below freezing, and plenty of January afternoons reach the fifties. The problem is the night. The same normals count about 65 nights a year at 32F or lower, and the average January low sits right around freezing. A coat put down at noon on a 55 degree day is still soft at dusk, and a frost that night on an uncured coat leaves it weak and patchy. So winter is for repairs, paving plans and quotes, not sealing.
Both work well here, for different reasons. A spring coat goes on before the long run of hot days and takes the UV that would otherwise go into bare asphalt all summer. A fall coat goes on after the summer has opened up whatever cracks it was going to open, so the crack filling catches all of them, and the drive goes into winter sealed against the freeze and thaw nights.
If you are choosing, fall is usually the slightly better argument for a drive that already has cracks, and spring for one that is sound but has gone gray. Midsummer is fine too, it just needs earlier starts and more flexibility about the day.
The evening before, the forecast gets checked for rain chances through the following afternoon and the overnight low. The morning of, the surface is checked: dew on a shaded drive in October has to burn off first, and a drive still wet from a night storm waits. If a storm cell is building on the radar, the job moves. Moving costs you nothing and the price does not change.
Sprinklers matter too. Irrigation systems are common in Triangle subdivisions and a zone that runs at five in the morning onto a fresh coat undoes a day's work. Turn them off for a day either side.
Hot mix asphalt has its own temperature limits for laying and compacting, and plants set their own hours. In practice paving here runs most of the year outside the coldest weeks. A new drive then needs six to twelve months before its first coat of sealer, so a drive paved in spring is usually ready to seal the following spring. The paving page covers that side.
