OK in still air incubators the air is warmest closer to the top. So if you have your thermometer standing up, it is reading the air temp that is closer to the top. If you lay it on its back, it will read the temp on the rack where it is laying. So you should have 2 different temps. You want the temp when it is laying on the bottom to be 99 degrees.
If you get it 99 at the bottom, then stand the thermometer up, it will be 101 maybe as high as 102. So if you are going to lay your eggs on the bottom, then lay your thermometer on its back and read the temp that way.
Got it! Thank you!
