You’re likely painfully familiar with the hottest, stickiest stretch of the summer, dubbed the “Dog Days” — but you might be surprised to hear that it has nothing to do with your panting pup.

Instead, you need to look to the night sky for the reason behind this age-old moniker.

The origin story

During summer’s peak heat, ancient civilizations noticed that a certain star made its appearance each year.

This star, Sirius, is also known as the Dog Star and is the brightest one in the sky, besides the sun.

The Greeks believed that the brightness of the star intensified the sun, making the summer heat even more unbearable.

Hence, the period was nicknamed the “Dog Days of Summer.”

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While they weren’t correct about the star’s effect on the Earth’s temperature, the name has stuck around to this day when referring to the notoriously hottest parts of the Northern Hemisphere summer.

When are the ‘Dog Days’?

Traditionally, the “Dog Days” run from July 3 to Aug. 11 because of the intense heat and humidity.

However, it’s important to note that Mother Nature doesn’t always play within this timeframe.

If you want to spot Sirius yourself, it often doesn’t make its first appearance in the dawn sky until the middle of August. 

And, depending on your location, your hottest day of the year may actually fall before or after this period.

Your hottest day of the year

While much of the country does usually see their hottest day of the year in July or early August, there are a few outliers worth noting:

• Desert Southwest: The hottest time of the year falls a bit earlier for locations in this region. You can typically count on the most intense summer heat throughout June or very early July for the Southwest before the monsoon moves in and cools the temperatures down a bit.
• West Coast: On the flip side, much of the West Coast usually sees their hottest day after the "Dog Days" in late August, September or even early October. In the heart of summer, onshore winds keep low clouds, fog and cold air in place along the coast. But as we head into September, we see a shift in the wind pattern that brings hot, dry winds from the interior to the coast and then offshore.

Caitlin Kaiser graduated from the Georgia Institute of Technology with both an undergraduate and graduate degree in Earth and Atmospheric Sciences before starting her career as a digital meteorologist with weather.com.