This template is an experimental helper for {{Climate chart}} - whenever possible, use that one directly, rather than copy-pasting from wikipedia. This is basically just a wrapper that can easily convert wikipedia weather box tables into a climate chart.
If you see a horribly broken climate box, likely you need to replace "rain mm/inch" for "precipitation mm/inch" in the table. For example:
|Jan rain mm = 43.8
|Feb rain inch = 4.40
to
|Jan precipitation mm = 43.8
|Feb precipitation inch = 4.40