Winter Tyres

On monday I took our car to the Workshop where we had the Winter Tyres fitted. ( Law here, if you have an accident or such between November and April and no Winter Tyres or M+S, then the Insurance won't pay) It was a bit chilly then but today we have over 17° and sun! Just like a summer day, better than lots of summer days! Anyway done now, so a cold snap won't catch us out....
I wonder if that is why in UK an inch of snow or minus 2°C sends the country into chaos? No Winter Tyres, you are still slipping about on Summer ones?Which just do not grip under 7° C, could be..........