The cold will be more taxing on a battery, but if you get a nice quality batt with a large capacity MAH you should survive the day just fine.
If your AEG does get wet I would recommend giving it a good wipe down when you get home, if you have the knowledge, take it apart down to the mechbox and give everything a good once over with a nice dry cloth.
__________________
"Its only a little bit on fire"
|