Route saw snow and freezing temperatures overnight
The Mountain Road and the upper section of the Tholt Y Will Road are to remain closed until at least midday tomorrow (Thursday 20 November).
The Isle of Man Constabulary confirmed the decision has been made 'for the safety of the general public as well as for those maintaining the roads and those responding to incidents'.
Officers reiterated the 'closure is enforceable, and entering closed roads is an offence'; adding 'please don't put yourself and others at risk'.
The Creg Ny Baa back road is said to be 'passable with care for four-wheeled vehicles but dangerous for motorcycles'.
Meanwhile, a yellow weather warning for frost and ice will remain in force on the Island until 3pm on Friday (21 November).
Taxi fares on the Island to rise
Bus Vannin warns of services at risk this evening
Weather causes changes to today's sailing schedule
Kewaigue closure in place this weekend for manhole replacement
New Captain of the Parish of Arbory appointed