The exact dates of the Dog Days can vary from source to source, and because they are traditionally tied to the dawn rising of Sirius, they have changed over time. However, most sources agree that the Dog Days occur in mid-to-late summer.
Here at the Old Farmer’s Almanac, we consider the Dog Days to be the 40 days beginning July 3 and ending August 11. These days occur soon after the summer solstice in late June, which also tends to be the beginning of the worst of summer’s heat.