Perhaps one of those heat sensor guns (Harbor Freight comes to mind as routinely having them on sale) could take a cold reading then another reading a few minutes later?

__________________
Become a BMW CCA member! Click HERE to join and feel free to use my BMW CCA member #191509 as a referral.

• 2015 f06 650ix GC (Moonstone exterior/Cohiba brown Merino Leather interior)
• 2014 f15 X5 50i (Space Gray exterior/Mocha Nappa Leather interior)