clear-day.png
clear-night.png
rain.png
rain-night.png
snow.png
sleet.png
wind.png
fog.png
cloudy.png
cloudy-night.png
partly-cloudy-day.png
partly-cloudy-night.png
chance_of_rain.png
chance_of_rain-night.png
chance_of_snow.png
chance_of_snow-night.png
chance_of_storm.png
chance_of_storm-night.png

Possibly supported in the future:
hail.png
thunderstorm.png
tornado.png