The weather in Wheaton can change quite quickly. In order to determine whether the Observatory will be open, we use several tools to monitor our weather. We also have our own weather station that gives us even more accurate weather data.
Clear Sky Chart
This image shows the sky conditions for today and tomorrow. The top row (Cloud Cover) is the most important one and gives an estimate for how much clouds there will be in the sky. The darker the color, the less clouds there are forecasted, and the better the observing conditions will be.