Why does this happen? When its sunny the next day it starts right up.

When was the last time the spark plug wires where replaced?

Right on plug wires or possibly coil pack are prime suspects. Sometimes if you get it in a dimly lit area and watch under the hood while cranking when it won't start or when misting the area with a spray bottle of water you will be able to see the blue spark arcing off a plug wire or the coil pack. In an emergency if you can wrap a couple layers of electrical tape around where you see the arc that may get you through until you can replace the faulty component(s).