This was the only add-on that came up for calendar weather. It works fine as long as you don't have any events planned for the day which is why you would need to check the weather. The temperature is blocked by any event you may have for the day. It would be nice for the temperature to be displayed in the lower left corner instead of the upper left corner so that it could be visible on days you have a few things planned.
This review is for a previous version of the add-on (0.3.2).