It's tough to pick a temp that works across all your devices because each device will be different depending on the model and location within the room. There's another thread out there where they recommend using the TemperatureThreshold OID, instead of the raw temperature information: See here. I've used this method and had good luck getting alerts when the AC went out.
Thanks for your Help and advice.
After looking through Cisco Datasheets the Normal operational Temperature for most Cisco devices are :
2960 23 to 113°F (-5 to 45°C)
2950 32 to 113°F (0 to 45°C)
3750 32 to 113°F (0 to 45°C)
3560 32 to 113°F (0 to 45°C)
So i have decided to do WARNING at 50c and Critical Alert at 60c - Using customer poller - ciscoEnvMonTemperatureStatusValue
Example of alert