Temp diffs from lid to cooking grate


TVWBB All-Star
I just got my 18.5"wsm back in feb this year, and I've had some real big temp differences from what the lid is telling me to what my other temp probe is telling me(about a 10" probe down the lid vent). I've tested both of these gauges, and my Maverick remote, in boiling water, and they were all about the same. When on a cook the Mav and the 10" were on, but the lid was 30-60deg off (on the low side). So I called Weber, and they sent me a new one, and it was very close to the other two, but now I'm having the same problem. So my question is: Are the temp gauges that come with the wsm that bad, or is there just a lot of difference in temp inside that cooker?
BTW- on my last pork butt cook I was having this problem and I just went off of the 10" gauge, but at end of my cook both the lid and the 10" where spot on. Whats going on with my temps?

Kevin Kolman

Have not heard of these kind of issues occurring continually with someone using a bullet. Although, the amount of food, water and excess build up on the smoker can cause temperature fluctuation these seem a little out of the ordinary. Weather can also cause temperature differences inside our cookers. Understand that I do not necessarily us a thermometer as gospel, it is more as an indicator of what is going on in the smoker. Although we would like them to be perfect all the time, climates and conditions are never the same. The thermometers a good but there will always be a human element that I believe makes things fun.


J Hoke

We use WSMs in competition and have found there will be a pretty big difference in the lid thermometer and grate at the start of a cook, but the differential decreases with cooking time. Eventually they get pretty close. Don't really know why unless it has to do with the way the heat circulates in a WSM.
There may be a difference between lid and grate temps, but also the WSM dome gauge is unreliable. Mine is always off at least 25 degrees under the actual temp.

Meathead says: "Most grills and smokers come with bi-metal dial thermometers, and they're usually crap. ... It is not unusual for this design from the 1800s to be off as much as 50°F.... You cannot trust them. I have readers tell me that when they bought a good digital from my list below that they learned their grills were off by as much as 100°F!"

He quotes Alton Brown as saying "Bimetal coil thermometers are about as accurate as a sniper scope on a nerf gun."