There is a chassisTempAlarm object-type inside the CISCO-STACK-MIB.my.
Does it help?
chassisTempAlarm OBJECT-TYPE
SYNTAX INTEGER {
off(1), -- temperature within normal range
on(2), -- temperature too high
critical(3) -- critical temperature, system
-- shut down imminent
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The chassis temperature alarm status."
::= { chassisGrp 13 }