Forecasters warning of black ice
The Mountain Road has now opened following the overnight snow but the Tholt-y-Will Road and the Brandywell Road remain shut.
Officers are advising drivers to go about their journeys with care, using main routes rather than minor roads, and warning motorists to be wary of ice.
Forecasters at Ronaldsway are predicting some further isolated snow or sleet showers later in the day, and have issued a yellow weather warning for ice and black ice forming on untreated wet surfaces overnight into tomorrow.
Isle of Man Transport has confirmed all bus services are running as normal.
The Department of Infrastructure's gritting teams were deployed yesterday and are still working to treat major routes.
Infrastructure officials say gritting teams are currently clearing snow and treating the Mountain Road and expected it to be open within the next few hours.