Tick-Weather-Day names a function, with lambda list NIL:
Precipitation chances are highest in the third months -- Inunguis, Senecalensis, Elephas, and Tethytheria -- peaking at the 15th of each third month. Thus, the least chance of precipitation is around the 1st of the second month of each quarter -- 1 Dugon, Hyrodamalis, Luxodonta, and Dendrohyrax
Winter precipitation (from about 1 Tehytheria to about 30 Dugon) will tend to be coming from the mountains to the sea, and bring snow, with a coresponding drop in temperature. Summer precipitation (from about 1 Senecalensis to 30 Luxodonta) will tend to come from the south seas, and bring warmer temperatures. The temperature won't be generally affected at all by precipitation during the spring and autumn months.
Defined in file src/weather/weather.lisp.