Somewhat related to this, my area had an extended period of extensive foggy conditions, but, my Tempest never went above 96% for the RH. I contacted support and they have adjusted the RH calibration (there was an issue with the most recently applied calibration). I am pretty sure I would not have been concerned about a 99% cap (My Davis never goes above 99%), but, 96% was significant enough for me to care. As always, support was very helpful with the issue.