Partly cloudy and partly sunny?
Like so many viewers, Patricia Thorpe of Elliot Lake Ontario wants to know the difference between partly sunny and partly cloudy. These two terms are among the most poorly understood of all weather terms. Forecasters have been hassling over the definition of “partly” for years; that’s why it is not widely used. In forecasting sky conditions, meteorologists describe what percent of the sky, from horizon to horizon, rounded to the nearest 10, is expected to be covered by clouds. A sunny day is one when there are no clouds or only 10% of the sky is expected to have cloud. With 20% or 30% cloud, the forecast calls for mostly or mainly sunny, or sunny with cloudy periods. When more cloud than sun is forecast, say 70 to 80% cloud, it’s mostly or mainly cloudy or cloudy with clear periods. When 90% or more of the full sky is covered by cloud then it’s a cloudy or overcast sky. When it’s about half cloud and half blue sky, the wording is mix of sun and clouds or variable cloudiness. The Weathe
