Chazz Ludwin of Rosedale wonders: "When and how were the original normal temperatures obtained? And does it take into account the weather patterns in the years/centuries before?" "Normal" suggests weather "as it should be." We should say "average," which implies variation is normal. For Baltimore, the National Weather Service uses a 30-year average of BWI temperatures, recalculated every decade. The current averages are based on 1971 to 2000. The next, beginning in 2011, will use data from 1981 to 2010.
FRANK ROYLANCEThe Baltimore Sun