Blair will step up as interim head coach while Gregor Townsend is on British & Irish Lions duty in South Africa.
Scotland A will play in late June, with the opponents yet to be confirmed, before a full team take on Romania on July 10 and Georgia seven days later.
Blair, who will be supported by the SRU’s director of high performance Jim Mallinder, said: “I’d like to thank Gregor and Jim for this opportunity to lead the Scotland summer tour and I’m looking forward to continuing to build the positive culture and results we have achieved in recent months.
“This tour gives us the chance to work with a wider group of players and see how they can step up into the international game, whilst also continuing to look to improve with our established Scotland players.
“The three matches will present very different challenges and as a squad and coaching group we will be looking to continue to create depth and competition for places within strong team performances.”
Townsend has been recruited as Lions attack coach for South Africa and he will be joined on the tour by Scotland defence coach Steve Tandy.
Several Scotland players are also expected to be selected by the Lions.
Blair, who has been part of the Scotland coaching group since 2017 as assistant coach specialising in attack, will have support from national forwards coach John Dalziel and scrum coach, Pieter de Villiers.
Peter Murchie, the Glasgow Warriors assistant coach, will also join the coaching team on tour, along with Mallinder.