We're in the dog days of summer now
We can officially say it! We’re in the dog days of summer! It’s hot, the humidity is high, and we’re all baking with a high heat index.
The origins of the phrase “dog days of summer” have nothing to do with the weather. The dog days of summer coincides with the rising of the star Sirius. I don’t mean Sirius from Harry Potter, rather the star within the constellation Canis Major.
Between July 3rd through Aug. 11th, Sirius rises in conjunction with the sun. A conjunction occurs when an object passes between the earth and the sun. The ancient Greeks and Romans believed that the combined energy from the sun and star aligning would make the weather hotter. The rising Sirius was associated with times of drought, unrest, and bad luck. Essentially, during this period, people and dogs would go mad because of the heat. Hence the phrase “dog days of summer.”
What causes the heat?
Sirius is the largest star in the Canis Major constellation and is the brightest star in the galaxy. If you were to place the star next to our sun, it would appear 20 times brighter.
Despite how large Sirius is, and its conjunction with the sun, the energy from the star has no impact on our seasons or the hot weather. The tilt of the earth is what causes the seasons.
During the year, different parts of the earth receive more direct sunlight as they tilt towards the sun at an angle of 23.5°. More direct rays plus the longer days lead to hotter temperatures.
Late summer is typically the hottest because heating is a cumulative effect. On the Summer Solstice, which occurs in late June, we receive the maximum amount of solar heating. Because of the cumulative effect of heat, we may not see our peak summer temperatures until much later. After the Solstice, heat input during the day is still greater than the cooling rate the earth undergoes at night.
The hottest day of the year varies by location varies by location
as well. All states and cities have smaller-scale factors influencing climatology and when they experience their hottest temperatures.
In southern Arizona and New Mexico, their peak summer temperatures occur between June 16th-30th. Here in southwest Missouri and Arkansas, our peak heat isn’t until the first week of August. Now look at Texas, their peak isn't until mid-August, while the Pacific Coast, their peak heat is in September.
Following the star - Here’s how to find Sirius
Sirius is easy to spot in the night sky. Find Orion’s belt which points downward towards the star. Sounds like the same way to find the North Star right? Sirius and the North Star are the same.
Are we in a heatwave?
While it is hot, we are not technically in a heatwave. Our average temperature this time of year is about 90°. Most of the forecast calls for temperatures sitting right around climatology.
There is no formal definition of a heatwave, and the criteria may vary depending on the location or country. The World Meteorological Organization defines a heatwave as five or more consecutive days where the high temperature is greater than the climatological average by 9°F. The National Weather Service defines a heatwave as a spell of anomalously hot, humid, and uncomfortable weather lasting two days or more. The NWS definition is open to more interpretation.
How long will the heat last?
With a cold front forecasted over the weekend, it looks like we’ll have relief from our hot stretch by Sunday. The heat may come back again. Longer-range temperature outlooks still have us in the region of above-average temperatures through Aug. 9th. Even September tends to be hot. Until that first strong fall cold front comes through, you can expect many more hot days ahead.