Why is it raining on board the Nostromo when Brett is looking for the cat?
The Nostromo had just spent some time on LV-421 with its landing gears deployed. The climate on the planet was harsh and seemed to have a lot of rain and ice. Hence, one can deduce that the landing gear had collected ice and water from its stint on the surface, and that Brett is in the landing gear compartment when he appears to be rained on by various drips from melting ice and what not.
