The only way to know for sure what your grate temp is, is to monitor it at grate level. How close to the grate is the thermometer?
Team: Smitty's Real Pit BBQ
Superior SS-3 - Courtesy of Gainesville Jaycees and Superior Smokers
2 Custom Built Reverse Flow Stickburners
Weber 22.5" WSM
Weber 26.75" OTG
Weber Blue 2000 Stainless Performer
Weber Red 1998 Stainless Performer