EdP;
I have been using remote therms for several years. I have learned that laying a probe on a steel grate will normally give a higher temperature. It is probably not measuring the air temperature but the steel grate temperature. Use a grate clip that most probes come with and that will give you a more "normal" reading. Steel grates absorb heat and commonly are hotter than the surrounding air.
As a possible matter of interest, I place my grate clip so it is pretty much at the same level as the meat, but far enough away from the meat that the "cold" meat won't adversely affect the therm temp. At the same time, you will need to keep the probe away from the outside of the grate as the heated air coming up from around the deflector adversely affects the probe causing too high a reading.
I hope that is helpful...
Keep on smokin',
Dale53