I found out that iguanas love to heat up very high. When I finally provided high temps, they used it avidly.
Materials in the center of the basking spot gain heat from the radiation from the heat source. They get hotter than the actual temperature of the air. Check this out by putting a heavy metal object like a heavy cast iron frying pan in direct sun. If the outside temperature is 95F, the metal will get up to over 150F.\
If a thermometer is placed in the center of the hot spot, it will gain heat and give a falsely high reading.
From your post, I think you are using a point-and shoot thermometer, hopefully it uses a laser dot. The temperature you get is of that spot on the substrate which has gained heat. I found the best way to check the heat is to put a 5 inch X 5 inch square of slightly wrinkled newspaper in the center, and then check if it reads 145F. It has to be wrinkled because it can't be laying against any substrate that has absorbed heat. It would be better to lay two 1/2 diameter by 4 inch dowels on the substrate, with the newspaper on top suspended over the substrate,, and read that temperature. 145F was my iguanas' magic number, which always pleased my iguanas who luxuriated in it, and I watched them very carefully at first to make sure there was no harm done. They basked and heated up, then moved away to lower temperatures, and then came back for more. Direct laser point temps of my iguanas' skin was around 100-103F when the newsprint was at 145F. So, iguanas gained heat to 100F, while the newsprint reached 145. The newsprint became my hot-spot temp checking method. From then on, I used the newspaper method to get the basking temps just right.
I now you already know this so please forgive me for "talking down' to you. But when igs use a high heat basking spot, I just assume really, really need to be able to retreat to an area that is in the low 80's to the mid-70's.