At least 130,000 people are expected to travel to the showground, on the edge of the town, from today until Thursday.
Highways England has warned that traffic is busier than usual, and asking motorists heading for the show to plan for delays.
Andrew Charnick, emergency planning officer for Highways England in Yorkshire, said: “While we at Highways England do all we can to alleviate congestion on the major routes to the event and keep traffic flowing, obviously it will be busier than normal in this area.
“We work very closely with partners including the police to ensure people travelling to events can get around as smoothly as possible.
We are advising road users to plan their journeys into Harrogate – that might mean a simple check for congestion before leaving the house, delaying their journeys or even opting for a different mode of transport on the day.
“We have a lot of experience of handling events like this and have tried and tested systems in place. We work with our emergency service colleagues to ensure those heading for the event get there with minimum fuss and delays.
“Motorists not planning to attend the show should plan ahead and leave extra time, and check our Twitter feeds and website for the latest information to ease their journeys over that weekend.”
Drivers can check travel conditions before setting out on journeys. Highways England provides live traffic information via its website at www.trafficengland.com