The temperatures are normally way higher than in Sweden but the air contains a lot of humidity and especially southern stages closer to the sea can feel a lot colder than they are. The temperatures also usually vary a lot. I experienced a range from -10 to +15 in one edition with snow, sun and even rain or fog. You won't make a mistake if You prepare for Sweden and Wales combined with some suncream on top, i.e. to be prepared both for cold and rain (to have spare clothes and shoes in case they become wet). If it's not needed You can always leave it in the car.