One of the decisions that I have to make is calling a rainy day recess. Basically if it is raining significantly during our lunch time recess, we do not send the students out for recess, but rather call a rainy day recess. A rainy day recess consists of various indoor activities for students during lunch. This involves the movement of students to various locations such as our library, our gym, our technology lab, the music room, and classrooms. Basically rainy day recesses are harder to organize and involve the moving of students from the cafeteria to their particular rainy day recess location. It is a lot of work.
For the past few years I have been using an iOS app called Dark Sky to help me with my decision making process regarding whether to call a rainy day recess or not. Dark Sky is an app that provides a macro forecast for a particular location and provides a visual representation of the probability of rain or snow for the upcoming hour. It calls upon local weather stations to predict precipitation for your particular location. From my experience it works very well. I use it daily in the winter months to help make the rainy day recess call.
A companion web site that provides similar information is called Forecast.io. I highly recommend both.