[A Little Short]

I need to paint my deck rails, which are PT and have dried out enough to paint. The weather is supposed to change this week with the temps dropping. It is supposed to frost a couple of nights. Should I wait until after the frost warnings to paint? It's supposed to warm up at the end of week, into next week.

 

[mark sr]

It would be best to wait until the danger of frost is past.

 

[stick\shift]

Also, not what you asked, but I would use a solid body stain instead of a paint; the maintenance is a little easier.

 

[consideritdone.na]

If you do decide to paint, use a shellac based sealer to seal any knots and to prime the wood.

 

[mark sr]

While pigmented shellac does a great job at sealing knots and stains I wouldn't use it for an over all exterior primer, it's ok for spot priming but an exterior oil base primer would be better for priming it all.

 

[A Little Short]

Does Arborcoat stain need a primer?

 

[mark sr]

About the only time a stain needs a primer is when tannin bleed is expected ..... and that is mainly with cedar, shouldn't be an issue with pressure treated pine.

 

[stick\shift]

It's not the stain that needs the primer, it's the wood - you are trying to seal the wood surface so materials in it don't bleed out and through your finish.

 

[Calson]

I need to paint my deck rails, which are PT and have dried out enough to paint. The weather is supposed to change this week with the temps dropping. It is supposed to frost a couple of nights. Should I wait until after the frost warnings to paint? It's supposed to warm up at the end of week, into next week.

I would wait for spring and give the PT more time to dry out completely. It takes so much time to paint deck rails that I would not want to do it now and then have it fail and need to sand and repaint.