The Department of Infrastructure says bad weather means the Mountain Road won't reopen tonight.
It says work to prepare the route for TT has been delayed because of the wet weather.
The Mountain Road had been due to reopen at 10pm but will remain shut between the Bungalow and Creg Ny Baa overnight.
The DOI says it now hopes to reopen the Mountain at around 4.30pm on Wednesday - but says bad weather may mean more delays.
Illegal immigrant turned back at Manx border can't stay in UK
Bank scammers warning as calls target Island residents
Island to extend UK VAT cut on power, says Treasury Minister
Woman thanks mystery van driver after daring sea rescue
Stay off damaged slipway in Laxey, says local authority
MHK sues attorney general and returning officer over election votes
Islanders reminded to keep challenging domestic abuse beyond October