Meaning : It means the hottest period.
Dog Days of summer indicate the hottest sultry period of summer.It is also used to indicate the period of inactivity or stagnation or lack of progress.
Origin: The name was given after Sirius, the Dog Star (in latin canicula),the brightest star in the heavens besides the Sun.Hence Dog Days are also called as canicular days.
1)When the hot days come, I think they might remember that those are the dog days, and use water carefully without much wastage.
2)During the dog days,it's hard to get much work done.
3)Every winter there's a week or two of dog days when sales drop dramatically
4)The costs of coolers are high due to the dog days of summer.