You leave them outside uncovered? If so that's a bad idea.
Our locos are left outside during the summer, but are always covered when we are not running them. Covered by either plastic storage bins, in the roundhouse, or wrapped with heavy grade plastic over a bridge like in this photo:
Even the slightest bit of moisture can destroy complex or even simple circuitry inside a locomotive. And temperature extremes can also cause a great deal of problems.
But it doesn't sound too bad. Thankfully LGB smoke units are replaceable for the most part.