How can I prevent the anti-theft system from engaging while vehicle car is off?

The anti theft is part of the programming in the computer; There is something, probably due to weather conditions, causing the alarm to go off. A door ajar sensor could be faulty and showing open when it's not open. The only way to be sure is to unhook the battery until some diagnostics can be done. I have seen some under hood fuse boxes fail causing circuit issues, but without testing and duplicating the symptoms it would be hard to say what the cause is.