Weather conditions
The application and performance of paints and varnishes is affected by the conditions under which they are applied. Exterior coatings should not be applied when there is risk of rain. All coatings, particularly water-borne types, should not be applied when the ambient temperature falls below about 5 ^oC or the relative humidity rises above about 80%. In very hot conditions, or in direct sunlight, the solvent may evaporate too quickly causing difficulty in maintaining a "wet edge", affecting the join between successively painted sections. If exterior painting is undertaken in conditions when overnight frost or condensation is likely, this should be timed to allow a reasonable period of drying before nightfall. High winds may carry dust or grit on to wet painted surfaces