Iodine is used throughout your body. The body contains about 1500 mg iodine, and it's in skin, muscles, fat, and organs. Everywhere. So you can need iodine and still have a perfectly normal temperature, if you're getting just enough iodine to support your thyroid. Without taking iodine, I had a normal temperature for years -- until I didn't.
A true basal temp of 98.6 is too high. If you're not experienceing symptoms of being hyperthyroid, I'd suspect your technique is flawed, or you're snuggled under the covers and you're toasty warm and you slept late. I prefer temps taken during the day when I'm active, with an aim to reach an average temp of 98.6 from temps taken 3, 6, and 9 hrs after I get up.