Road closures and diversions are in place with signage in affected areas.
The following major roads have been affected: A52 at Radcliffe on Trent between Bingham and Stragglethorpe; A52 Wheatcroft Island; A60 Leapool Island, Mansfield; A46 at Bingham at the Saxondale Island and the A6097 slip road A617 Pleasley Hill.
One of the worst affected areas is the Main Street area of Lowdham.
Other affected areas include Linby, Sutton in Ashfield, Sutton Bonnington, Lambley, Hucknall and Watnall.
Police are advising: Only travel if it is essential; Check traffic updates; It takes longer to brake in wet weather so leave plenty of space; Follow advice on road closures, diversions and the advice of police, fire and other officials; Do not walk or drive through flood water as there could be hidden dangers.
Superintendent Paul Burrows said: “Nottinghamshire Police has received a number of calls about the overnight flooding and I would like to reassure the public that a joint police, fire, ambulance, council and highways response is now well underway to help keep people and their properties safe – and help keep disruption to an absolute minimum.
“I would encourage people to only travel if their journey is absolutely necessary and to check local news, weather and traffic updates before they travel.
“We have declared the flooding to be a major incident and are, of course, continuing to monitor the situation as it unfolds. We are continuing to follow weather forecasts as part of our ongoing response to the significant amount of rainfall we have seen overnight.”
Only call 999 in an emergency where there is an immediate threat to life or if there is a crime. For all other non-emergency matters, please call Nottinghamshire Police on the 101 non-emergency number.
Live traffic updates are available on the Highways England website: www.trafficengland.com, Nottinghamshire Police on Facebook, @NottsPolice on Twitter, Nottinghamshire County Council on Facebook and @NottsCC on Twitter.
Your district or borough council may also help on Facebook and Twitter.