Police closed the northbound lanes of the highway between County Road 93 and Line 2 in Oro-Medonte, where the collisions occurred on Sunday afternoon amid high winds and blowing snow.
Three people suffered minor injuries in the collisions, OPP Const. George Silvestri said Sunday.
The northbound lanes of Highway 11 reopened at about 3:45 p.m.
Elsewhere in the province, a 100-kilometre stretch of highway was closed Sunday afternoon between Ottawa and the Quebec border because of dangerous conditions.