Posted on July 23, 2015 by Geneva Gray
Y'all, it's hot outside! Just this week, heat index values stretched into the triple digits across North Carolina. It is hot enough to make even the most active dog lethargic from the heat. Yes folks, we are in the dog days of summer.
Every few weeks, our office receives a question or two about North Carolina's climate. These questions filter through our Ask a Meteorologist database. A few years ago, a resident of Chapel Hill asked us:
"When do the dog days of Summer begin and end? How did it get that name?"
It turns out the dog days are more than just a linguistic turn of phrase. They are a distinct time of year ranging from July 3rd to August 11th (40 days) and correspond to when the star Sirius (aka: the Dog Star, part of the Canis Major constellation) rises with the sun. Ancient stargazers noticed that Sirius rises with our sun during the hottest times of year. It was thought that this bright star somehow contributed to the warmth experienced during these hot, summertime days.
Sirius is too far away to contribute to any sensible heat we feel here on Earth, but this does lead a curious climatologist to ask several questions! What are the hottest and most humid 40 days across NC? And do the astrological dog days line up with what we experience in NC? The answers to these questions are shown in the map above.
These climatological average "dog days" are calculated using high temperatures and humidity measurements from the last 30 summers. Each circle on the map is centered around the local weather station where temperature and moisture measurements are taken. Lighter colors correspond with an earlier average occurrence, while the darker red colors indicate the overall average occurs later in the year. Clicking on a circle will reveal a location's dog day date range.
The values across the entire state are close to the dog day time period of July 3rd through August 11th. Only one location in Clayton, NC has that exact time range, and there are several others that are only different by a day or two. Overall, 10 of the 15 locations have a calculated range that occurs earlier than the astronomical dog days! Hatteras Island is the lone location that peaks much later than the rest of the state. This is largely due to it's proximity to the ocean.
Explore the map above to see what the hottest average stretch of days are near you. Does this line up with your experiences? Ask us more at our Ask a Meteorologist webpage!