Hello,
If I'm looking at the mib correctly, the following OID provides "extremeCurrentTemperature" in Celsius. .1.3.6.1.4.1.1916.1.1.1.8.0
You should be able to poll this location for the temperature information.
I should mention that this is a very old switch running older software that is no longer supported by Extreme Networks. I can't make any promises that this will work 🙂
-Drew