Rainfall during the first half of August varied widely, from less than 25% of normal in New England to more than 200% of normal in southeastern parts of the Northeast. Of the 16 drier-than-normal major climate sites, eight ranked this first half of August among their 20 driest on record. Almost all of New England was either abnormally dry or in a drought. Of the 19 wetter-than-normal major climate sites, 11 ranked this first half of August among their 20 wettest on record.
A major source of rainfall for wetter-than-normal areas was Tropical Storm Isaias on August 4. The greatest rain totals ranged from 4–9 inches, with Allentown, PA, having its wettest August day with 4.92″ of rain. Significant flooding occurred, particularly in southeastern Pennsylvania where several waterways recorded their highest water levels on record. Some of the same areas that received excessive rainfall from Isaias saw more heavy rain and flash flooding from August 6-7 and August 12-13.
Temperatures continued to be above-normal during the first half of August for most areas, ranging from near normal in western parts of the Northeast to more than 6°F above normal in parts of New England. All 35 major climate sites had a warmer-than-normal first half of August, with 26 ranking this August 1-15 period among their 20 warmest on record.