With SNMP you should alert on the data relevant to your setup. If 40 degrees is unusual, then you should alert on that. :)
If you need some information about the hardware in the ASA, then you could see this post that I made, and then look up the numbers on Intel's website.
https://communities.cisco.com/community/technology/security/ngfw-firewalls/blog/2016/02/02/asa-hardware-facts-sheet