I have a 2006 Suzuki Forenza station wagon and the past few winters the cars alarm will go off and on when it drops below freezing?

when it rains

That's nice. Did you want to ask a question while you're here?

Adjust the hood switch higher up so that it puts more tension on the switch.

Many times an alarm will go off when the wind blows through the radiator and lifts the hood slightly.

Try pushing on the hood when the alarm goes off and on.

No fix, the alarm use many switches to be activated. One of the switches are being activated falsely or the switch is bad. A mechanic with a dealer level scanner can troubleshoot the fault.

https://www.youtube.com/watch?v=bPIYVknRRoc

mine goes off when it rains heavily. Can you lock the doors without turning your alarm on?

It may be reacting to a voltage drop, or the motion sensor is being tripped by wind gusts