Steam Summer Sale 2019 Date Leaked
As Steam Database has stated, Steam Summer Sale will launch on June 25 at 10 a.m. PST and will end in two weeks, on July 9. Information ragarding mini-games, Steam cards and coupons is to follow.
Another source has also shared the launch date:
2019 Summer Sale. Discount confirmation.
Don’t publish details of the sale in Steam communities or on your own website before the official launch.
2019 Summer Sale starts on June 25, 2019, at 9:50 a.m. PST and ends on July 9, 2019, at 10:05 a.m. PST.
Last year, the sale started a bit earlier, on June 21, and lasted two weeks as well.