Painting exterior walls when the atmospheric conditions are cool and humid can cause surfactant leaching These conditions are accelerated when applying paint just before or after a rain shower, or applying paint too early or late in the day.
The extended or slower dry time of the paint caused by those elements allows or causes the water-soluble ingredients (surfactants dispersions or soaps) in the paint to migrate to the top surface before the uncured paint film dries thoroughly.
To further exasperate the leaching the paint may be applied too early in the morning (before 10:00am) when the walls are damp from the morning mist, or if painted in the late afternoon (after 3:00pm). The evening dew will upset the normal during conditions of the paint.
In south Florida the leaching may only be a problem in our Winter season (January to March) because of the cool damp conditions particularly in the evenings.
Surfactant leaching will not cause damage or effect the durability of the paint. The leaching may wash away in a few days without treatment, or it can be hosed off with a strong stream of water from a garden hose.
Please review the following information on surfactant leaching. It is not a defect in the paint it is a typical issue, but we seldom experience it in south Florida. The unusually cold or cool weather this year is causing the leach.