The Prime Minister's Office says Harper plans to deliver remarks at the Cobequid Educational Centre after 7 p.m.
The riding is held by Conservative MP Scott Armstrong.
He will be challenged in this fall's federal election by former Tory MP Bill Casey, who is running for the Liberals.
Casey won the Liberal nomination for the riding of Cumberland-Colchester in March.
Casey previously represented the riding for 17 years, first as a Tory and then as an Independent before retiring from politics in 2009.
He was kicked out of the Conservative caucus in 2007 when he voted against the federal budget.