Choux that collapses after coming out of the oven has one of two problems: too much internal moisture, or a shell that was not set firmly enough before the oven temperature dropped. Both are fixable, but they require understanding what choux structure is actually made of.
The shell of a choux pastry is formed by steam pressure expanding the dough outward while the egg proteins set around it. If the proteins have not fully coagulated by the time the oven door opens, the steam escapes and the shell collapses inward. The fix is to leave choux in the oven longer than feels comfortable, and to prop the door slightly open for the last 5 minutes to let moisture escape gradually rather than all at once.
The egg ratio and why it changes with humidity
Choux recipes specify egg quantity by number, but eggs vary in size and moisture content. Adding all the eggs at once without checking the batter consistency is where most failures begin. The batter should fall from a spatula in a slow, thick ribbon and hold a V-shape at the end. If it is too stiff, the steam cannot expand it. If it is too loose, the structure has no integrity.
On humid days, the dough absorbs less egg before reaching the right consistency. Holding back the last egg and adding it gradually is not optional in variable conditions.