One of the dog days.
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.
The conjunction of the rising of the dog star with the rising of the sun was regarded by the ancients as one of the causes of the sultry heat of summer, and of the maladies which then prevailed. But as the conjunction does not occur at the same time in all latitudes, and is not constant in the same region for a long period, there has been much variation in calendars regarding the limits of the dog days. The astronomer Roger long states that in an ancient calendar in bede (died 735) the beginning of dog days is placed on the 14th of July; that in a calendar prefixed to the Common Prayer, printed in the time of queen Elizabeth, they were said to begin on the 6th of july and end on the 5th of September; that, from the restoration (1660) to the beginning of new style (1752), British almanacs placed the beginning on the 19th of july and the end on the 28th of August; and that after 1752 the beginning was put on the 30th of july, the end on the 7th of september. Some english calendars now put the beginning on july 3d, and the ending on august 11th. A popular American almanac of the present time (1890) places the beginning on the 25th of july, and the end on the 5th of september.
Source: Websters dictionary