Washington and many other cities have experienced a record number of warm nights this year

From Southern California to northern Maine, scores of U.S. cities have racked up more warms nights than ever previously recorded, as indicated by the frequency of low temperatures of 70 degrees or higher.

Washington has observed such warm low temperatures a record 85 times this year, compared with the normal of 57. Fifteen have occurred in September alone, a record for the month. And there are probably more to come.

Many locations along the East Coast have joined Washington in accumulating these warm nights in record numbers, including:

• Caribou, Maine
• Boston
• Salisbury, Md.
• Richmond
• Norfolk
• Wilmington, N.C.
• Charleston, S.C.

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For its part, Washington has seen a dramatic increase in its annual frequency of low temperatures of 70 degrees or higher, as shown in the chart below. A century ago, the District averaged half as many nights with lows at 70 or higher, compared with current times.