Where exactly are you placing the thermometer??? This makes a BIG difference.
If it is your "normal" thermometer you do NOT want to place it in the direct light (where your plants are). The thermometer is designed to measure air temperature (not radiant temperature from direct light). Tape the thermometer up on the wall with cardboard covering it (to shield it from light). And measure.
For AIR temp you want around 68-68ish
For RADIANT temp it can be 100-120 and be fine. The plants are design to withstand much more radiant temp due to their need of light rays.