The Heroes of the Storm ranked seasons have an average duration of about 3-4 months. Season 3 2019 will end on December 2nd.
It is impossible to predict the exact time of the day, so the countdown below is just an approximation timed to the midnight of the indicated day.
In the table, you can find the history of the starting and ending date of each season.
|Season||Start Date||End Date|
|S1 - 2016||Jun 14, 2016||Sep 13, 2016|
|S2 - 2016||Sep 13, 2016||Dec 13, 2016|
|S3 - 2016||Dec 13 , 2016||Mar 13, 2017|
|S1 - 2017||Mar 13, 2017||Jun 13, 2017|
|S2 - 2017||Jun 13, 2017||Sep 5, 2017|
|S3 - 2017||Sep 5, 2017||Dec 12, 2017|
|S1 - 2018||Dec 12, 2017||Mar 6, 2018|
|S2 - 2018||Mar 6, 2018||July 3, 2018|
|S3 - 2018||July 3, 2018||Sep 25, 2018|
|S4 - 2018||Sep 25, 2018||Dec 11, 2018|
|S1 - 2019||Dec 11, 2018||Mar 26, 2019|
|S2 - 2019||Mar 26, 2019||Aug 5, 2019|
|S3 - 2019||Aug 5, 2019||Dec 2, 2019|
Blizzard standardized the duration of each HotS season to about 3-4 months, so predicting the starting and end date of the future ones is quite simple.
Furthermore, before the start of each season, the developers also publish a blog post showing the estimated start and end date of the upcoming season. Note that the exact date may vary slightly by region, and sometimes they shortened or delayed it by about a week.
Header image: Blizzard