England, Wales and Northern Ireland will find out their group stage opponents when the draw is held in Paris today.
France has declared a three-month state of emergency after Islamic State terrorists murdered 130 people in the capital on November 13.
And thousands of migrants have descended on the port town of Calais in recent months in a desperate bid to cross the Channel.
Now the Foreign and Commonwealth Office (FCO) has launched a campaign to help supporters stay safe.
Foreign Minister James Duddridge said: “It’s never too early to begin your preparations, so we’re encouraging fans to do their research and stay up to date with our travel advice.”
He added: “Never before have we seen three home nations teams reach the finals of a European Championships.
“I am sure this will be reflected in the number of fans making the journey across the Channel.”
The 11-point guide offers practical advice such as planning ahead with accommodation, buying tickets from accredited outlets and taking out travel insurance.
But it also steers readers towards the foreign travel advice for France – which sets out the increased security measures prompted by the tragedy in Paris.
That advice says France is still facing “ongoing threats” by depraved terror groups including ISIS, also known as Daesh.
It tells British visitors to be “vigilant in public places” and “follow the advice of the local authorities”.