The cycle race covers 304 miles (490 km) split into three stages.
The event, in its third year, began as part of the legacy of the county hosting the 2014 Grand Depart for the Tour de France.
The men's race starts later in Bridlington, East Yorkshire later and ends on Sunday at Fox Valley in Sheffield.
The women's race starts in Tadcaster and ends in Harrogate on Saturday.
The race is jointly organised by Welcome to Yorkshire, the region's tourism agency, and French company Amaury Sports Organisation (ASO), which organises the Tour de France and other prestigious races in the European calendar.
Welcome to Yorkshire said the 2016 race attracted about a million spectators, generated about £60m for the local economy and was watched by 11.4 million TV viewers in 178 countries.
As in previous years, many of the towns and villages along the route have entered into the spirit of the race and decorated the roadside.
ASO race director Christian Prudhomme said it was "amazing"
He added: "In every village there are blue and yellow flowers, with bikes, with bunting and huge flags and smiles on everybody's face."
Welcome to Yorkshire's Sir Gary Verity said there was huge enthusiasm for the event.
"We have 2,500 volunteers this time compared to 1,200 last year.
"There is an increased level of interest in the event and we have been getting messages from people coming from all around the UK and beyond."
For spectators it is a chance to glimpse elite cyclists, including Olympic gold medal winner Owain Doull and former Women's Tour winner Kirsten Wild.
Frenchman Thomas Voeckler, who won the men's race in 2016, will also be defending his title.
Thousands of spectators are expected to turn out for the 2017 Tour de Yorkshire race which gets under way later.