Weather effects on paint curing

[foglights]

Is there a good time (season, time of day) to put paint on a weather exposed wooden deck?
Its summertime and it seems like a good time of year to paint the deck outside but I'm wondering how the weather (heat, humidity) will effect the curing of the paint. There is already a coat of paint on the deck so I plan on washing the dirt and painting right over the existing paint.
Thanks for any help.

 

[Ron]

It depends on the type of paint. There are many. If you are using a solvent cured coating, humidity doesn't really affect it (assuming you don't have direct condensation), but it will cure faster with increasing temperature. If the coating is water-based, high humidity will slow the drying time. Humidity has more of an effect on this type of coating than does temperature.

If the coating is a moist-cured urethane, then higher humidity is a good thing.

 

[TheTick]

Don't do anything stupid like putting latex over oil. I bought a house that received such treatment. Needed a full stripping after that.

 

[hokie66]

I would just avoid painting in sunlight. Makes it easier on both the painter and the paint.

Test the old paint to determine what type it is. If oil based, you need an undercoat. If acrylic, you can just apply the new topcoats, provided the surface is clean, of course. Acrylics are much better than alkyds for exposure to UV, but are not as impact resistant.