I have attached my version of weather_level_adj.py – if you place this in the plugins directory in place of the version that is already there, and make sure the new version is executable, then you will solve the problem.
Due to the restrictions on attaching files in this forum I have had to rename weather_level_adj.py to weather_level_adj.txt You will have to rename it back to weather_level_adj.py after you download it.
This version works but a better (more elegant and complete) solution has been proposed by ShawnHarte in this thread. Feel free to implement that instead if you wish.
The reason it calls wunderground so many times is that the error routine retries every 60 seconds. I have changed this in this version to every 1800 seconds to avoid the problem.