With three deaths already on open roads this week, the roads policing unit is issuing an urgent appeal to riders and motorists to take extra care.
They say that means travelling at the right speed for the road conditions and riding within your own ability.
Inspector Terry Stephen says the recent warm weather has probably tempted more riders than normal to go out for a lap.
And he's stressing that roads around the course can still be busy with traffic first thing in the morning.
MiCard users advised to take money out before the end of the year
Cards are 'hardwired' to stop working from 1 January
'Nothing else could have been done' to save some small fish at Clypse Reservoir
Manx Utilities confirms some died during draining process
'Come back to the table,' says DOI minister
Bus drivers on the IOM have voted in favour of industrial action
Consultation seeks feedback on changes to IOM first time buyer schemes
Proposals include adjusting thresholds and reducing residency requirements
Yellow weather warning for coastal overtopping
The west most likely to be affected