You should have your thermometer more or less at canopy-level.

It should also be under some shade... so it doesn't get direct light from the bulbs...

It should also have airflow around it... not stagnated air.

That should give you the true temperature.
turtle420 Reviewed by turtle420 on . radiant and normal temp my thermometer is at the level of the top of my canopy and in light. It was hot yesterday outside, so my grow room was hotter, the thermometer showed 95 which gave me a shock, so I left the door open to cool things down, it's now showing 82. is this radiant temp or normal temp? if so, what temp is it okay to go up to in radiant temp? Rating: 5