THE EASTERN STATES HEAT WAVE OF APRIL 20–28, 1957

Abstract

Temperatures during the month of April averaged above normal over practically all of the eastern half of the United States. Most States within the area east of the Mississippi River were either entirely or partially contained within the +2O C. anomaly isopleth. Most of the area of North Carolina, Virginia, Maryland, Delaware, and West Virginia was enclosed by the +4O F. anomaly, and a small portion of Virginia and Maryland was encircled by the +So F. anomaly isopleth [l]. These limited values do not in themselves confirm a pronounced and prolonged heat wave during this month. However, an examination of weekly anomalies in the Weekly Weather and Crop Bulletin [2] or in figure 3A in the article by Andrews [31 indicates that the monthly anomalies were definitely weakened by the subnormal temperatures present over the East during the first half of the month. The transitional period from below normal to above normal temperatures was of ephemeral duration. This was manifest by comments entered on the April Local Climatological Data forms and as specifically expressed by the Green Bay, Wis., Meteorologist in Charge: Overnight in the middle of the month weather turned from March type to late May type. Much of the East was under the influence of this heat wave throughout the latter half of the month and thus the semimonthly