When getting an early alpine start (3-5 am or earlier) it will probably be before the sun comes up. Hopefully, the weather will be better in the morning (that is often the point of an alpine start), but the lack of sunlight can make it difficult to see the clouds.
It usually possible to tell if there are clouds are not, by whether or not the stars are visible as well as whether or not the clouds are raining/snowing/sleeting or if there is fog, but observation options are limited compared to what would be visible if the sun was up.
Given these limitations, how would you assess the weather when getting a really early start?