A period of from four to six weeks, in the summer, variously placed by almanac makers between the early part of July and the early part of September; canicular days; -- so called in reference to the rising in ancient times of the Dog Star (Sirius) with the sun. Popularly, the sultry, close part of the summer.
DOG DAYS
Meaning of DOG DAYS in English
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012