Factory anti-theft alarm activates when vehicle parked in the sun on a 75 degree plus day

[Ibhipru]

Recently moved to an appartment and must park our Camry in an open parking lot.  When the sun is shining and outside temperature gets above 75 the anti-theft alarm goes off.  I shut it off by pressing the open door button on the FOB.  Then about one hour later, it goes off again.  It will continue to intermittently go off until the sun sets behind our building and the car is in shade.  The same is true if if there is intermittent sun and clouds but the alarm will not activate as frequently.  The alarm never acts up except in the presence of sun and warm weather. The car battery as well as the FOB batteries are good.  Any  ideas or suggestions would be appreciated.