Peeling exterior paint
Moisture gets in the wood and then the heat (and sun) will bring the moisture out to the surface. This causes the paint to blister and peel. 

Exterior wood (especially fascia hung away from a building) should be primed on all sides to keep the moisture out. 

You may need to protect the wood boards with a tarp until they are “dry”.  Pic a day when it’s not too humid. 

Often paint will peel if there is no interior moisture barrier. However, this is not your problem, because the boards are away from the house. 

You may need to check to see that rain is not seeping down between the roof and the fascia board. This could soak the wood and make the paint blister when the sun comes out. That’s why all edges need to be primed when dry.