Four higher altitude roads have been closed to traffic.
The decision in relation to the Mountain Road was taken at around 7pm today (Friday), due to a build up of snow and ice.
The closure, from Creg-ny-Baa to Ramsey Hairpin, will remain until at least 11am on Saturday.
Three other routes were closed about an hour and a half later, also because of snow and ice, and will be reviewed at the same time.
They are the Tholt-e-Will Road, from its junction with the Mountain Road down the Sulby; the Beinn-y-Phott Road, from its junction with the Mountian Road to the crossroads at Barregarrow; and the West Baldwin Road, from Injebreck reservoir up to the Beinn-y-Phott Road.
The Met Office at Ronaldsway says more snow will fall on the hills tonight, with several centimetres in areas above 800 feet.
Conditions are expected to improve during the night.