new top on a UDS keeping temps high?

SO I got a dome charcoal lit for my UDS as opposed to the barrel lid. I could not get the temp below 300. It was hot, and I used more wood chunks then normal but can't for the like of me figure out why the temp was so high? what do you guys think?
1. the new lid with added volume have something to do with it?
2, This was also my first smoke with the updated firmware. I have not updated since I built my heater meter 3 years ago. do I need to re-calibrate my thermometer?
3, I live in central IL, and it was hot yesterday, would the heat outside have something to do with it?

My bet is that you've got an air leak. Fuel + oxygen = heat. Ambient temp certainly does have an effect, but I'd be looking hard for an air leak before anything else.