The New Student's Reference Work/Dog-Days

Dog-Days is the name given in ancient times to the period of greatest heat in summer, because along the Mediterranean this is of nearly the same duration as that in which the rose at the same time with the sun. The joining of these two was supposed to have an evil influence on the earth. The period of the rising of the Dog-star with the sun is very indefinite and uncertain. In modern times dog-days are sometimes reckoned from July 24 to August 24, and sometimes from July 3 to August 11.