There's a second day of action in the TT tomorrow (Tuesday) and there will be an evening race.
It's due to the postponement of Saturday's racing, which took place today.
That will impact on the rush-hour and police are expecting severe traffic congestion in lower Douglas from mid-afternoon tomorrow.
Police are warning there is a real risk of traffic coming to a standstill and are suggesting anyone travelling to Douglas tomorrow should consider using public transport or sharing cars with friends or colleagues.
People are also being urged to plan their journeys home from work in advance.
The mountain section of the TT course will close at 11am tomorrow and the rest of the circuit half an hour later.
The Supersport Race 1 is due off at 12.15 tomorrow lunchtime.
There will then be two practice sessions, for the sidecars and the XGP, with the Superstock race scheduled to start at 6.30pm.
Course crossing points will be open for one hour between 5 and 6pm.
Roads will open from 8.30 tomorrow evening with the mountain section from Ramsey Hairpin to Creg-ny-Baa open by 9.30.