Clean, dry cracks and proper temperature are the keys to effective crack sealing. Sealant manufacturers typically recommend pavement temperature exceeding 40°F (4.4°C). If pavement temperature is lower than 40°F, it may be warmed using a hot air lance as long as the flame does not directly contact the pavement. Some agency specifications, like the Montana Department of Transportation, allow crack sealing in roadway temperatures as low as 35°F (1.7°C).
Ideally, the spring or fall is when crack sealing is most effective. These seasons are the time of year when cracks are moderately open, which allows for sealing cracks at their mid-point and not when they are all the way open or all the way closed.
Having a dry road is even more important than air or pavement temperature.
Be sure to inspect the cracks for ice or deicing material because they will negatively affect sealant adhesion and should be removed.