Dog Days of Summer

Pat Guinan
State Climatologist
Commercial Agriculture/University of Missouri Extension

The "dog days of summer" are in full gear in August with heat and humidity being the major weather makers for the Show-Me State. Where did the term "dog days of summer" come from? Typically, the term refers to the hottest and muggiest part of the season, but in reality we need to look to the heavens from where the phrase was derived.

The constellations are pictures of stars that we get when we "connect the dots" of stars. Examples include bears, (Ursa Major and Ursa Minor), also known as the Big and Little Dipper respectively, a scorpion, (Scorpius), fish (Pisces), and others, including dogs, (Canis Major and Canis Minor). The brightest star in the night sky is Sirius and is found in Canis Major, which translates to "the big dog." Sirius can be seen in the southern sky during the winter, but it is not visible during the summer season because it rises and sets with the sun. In ancient times our ancestors believed that extra heat was added to the sun when Sirius was in conjunction with it. It was believed this alignment brought hot and muggy weather. The period of time from 20 days before the conjunction to 20 days after was labeled "dog days." Today, the period between July 3 and August 11 is considered our "dog days."