Dog days of summer begin this week

Hottest time of year about to begin


The idea of 'dog days' goes back to before the birth of Christ. Ancient Greeks believed that the hottest time of year was due to two stars, Sirius and the sun. They thought that the two stars combined their energy to maker the earth hotter. We now know that no star give us nearly as much energy as the sun does.

Sirius is known as the dog star, hence the name 'dog days of summer.' Dog days runs from 20 days before Sirius rises in conjunction with the sun until 20 days after that time. While this time period varies by latitude, tradition states that the dog days run from July 3 to August 11. 

In order to see if this was indeed our hottest time of year, I researched temperature data for Roanoke, Lynchburg, Danville and Blacksburg. I split the data up into three categories. Pre Dog refers to data from June 1 to June 2. Dog refers to July 3 to August 11. Post Dog would then be data from August 12 to August 31. 

What I found is that the dog days period is indeed our hottest point of the summer for all four cities. 


I also found that more 90 degree heat was observed during dog days. For instance, in Roanoke an average of 26% pre dog days are 90 degrees or hotter, 36% of dog days are 90 or hotter and 25% of post dog days are 90 or hotter.


That's a somewhat complicated calculation, but I did it that way because each time period is different. Pre dog only goes for 31 days, the dog days period goes for 39 days and post dog lasts 20 days.

While we're on the topic of dogs, it's important to never leave a dog, human, or any living thing in a hot car. These summer days can turn deadly inside a car.


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