Dear bob88061, Weatheraardvark, and WeatherCat troubleshooters,
Just rebooted my iMac, macOS 10.13.2, and WeatherCat is the highest CPU usage with CPU Time 8:20 with uptime of 39 min. %CPU is running 13-58
How are you getting the CPU data - Activity Monitor? What does Activity Monitor show as other high CPU use applications? What you are observing isn't supposed to be occurring. The only think I can think of is that WeatherCat is having to reindex its data for some reason. If you have a lot of accumulated data that would explain the heavy CPU use.
At least on Sierra, Spotlight reindexes the file data on a reboot. I'm wondering if that index process is effecting WeatherCat in some way. Unless you have an running a SQL server, WeatherCat stores its data in text files that Spotlight will definitely index.
Sorry, that's about all I can think of.
Let us know if you uncover anything else.
Cheers, Edouard