This problem has existed for at least the last several versions. I am using a U.S. city. Here is how to reproduce it:
1. Wait until Weather.com no longer shows "today" but rather "tonight." It typically starts mid- to late afternoon for the designated city. This is important! The precipitation works properly until this time.
2. Configure Weather preferences in this fashion (not sure which element is the key one, so I'll reproduce everything):
The following items are checked:
a. Display temperature
b. Hide type
c. Display icon
d. View extended forecast
e. Show Weather Icons
f. Forecasts on one line
g. Show Meteorologist controls in submenu
h. Prevent Multiple Meteos from being launched
The following are unchecked:
a. Display city name
b. Display in submenu [current weather]
c. Display in submenu [extended forecast]
The number of days for extended forecast is set at "5."
Once the forecast on Weather.com changes from day to evening, the precipitation forecast for the remainder of the current day will ALWAYS read "0%" regardless of what it really is.