Monitoring air temps...whats the best method?

Newbe question I know but I haven't found any good, solid info on the subject...I get a 5-8 degree difference between under the lights temp and in a shadow temps...which is right? Also, where is the best place to monitor? Soil level, half way up the plant or at the tops? What is the best type of instrument for the best accuracy and rapid responce to temp?

First time grow indoors and I'm trying to learn the ropes...thanks in advance!

I measure the top of my tent, because heat rises and I have a ducted lamp hood with fan pulled air. I use a remote thermo/hygrometer in my tent with the base station display on my PC desk.. I can glance up and see what the temp and humidity are... I looked up once and it was 95! I went to investigate and damn inline fan for lamp hood quit working and the housing was hot as hell. That remote thermo saved me a lot of heartache..

I'm using a 4x2x6 ft metal storage cabnet that I have rigged up to grow. I am running an 8 x 4ft t5ho fluro setup and it does get hot when both banks of lights are on. I rigged up some cold water cooling to manage the temps and now have a handle on them but I need to know how to best monitor the temps the plants see in order to control the cooler.

I hang my temp and RH sensor about 6 inches below my air cooled light. Works fine for me.

You want to measure canopy temps directly below the light along with ambient enclosure temps. Ideally you would use an old school mercury or alcohol thermometer for ambient temp and one of these IR temp guns for canopy temps -