which season

For the equatorial stars, well, there are more of them in the summer. The circumpolar stars are also higher in the summer, so I would say summer. Still, the atmosphere might be clearer in the winter.

The equinoxes are often plagued with poor visibility due to storms.

Ah, I just made all that up, but it does sound kinda good, doesn't it.

Depends on where you are. Where are you?