Digital atomic wall clock showing the time of 7:04 PM, an outside temperature of 158°F, and humidity of 99% outdoors.
edit:
A replacement sensor is just over $20, but I found this (see below) for $15, so both my wall clock and the new one can read off the same new, full functional sensor. So now it’s fixed.
It’s weird that the new one does outdoor and indoor temp, but not humidity. The old one does outdoor temp and humidity, but not indoor temp. And the new one isn’t an atomic clock. I had to set it manually.
For the outside temperature, ensure the thing’s not in direct sunlight. For humidity, try taking the case of the thing apart and gently cleaning the sensor with isopropyl alcohol and a q tip.