Here are resources I use to help forecast the weather and astronomical seeing conditions at my observatory in Redlands, California.
Here is a graph showing current weather conditions at the observatory. These observations are recorded using a Boltwood Cloud Sensor.

The Clear Sky Clock is a service provided by Attilla Danko showing an hourly forecast of seeing. The San Bernardino County Museum is close to my location. The data for this forecast comes from the Canadian Meteorological Center. Special thanks to Attilla and CMC for providing these services.