My DC swim with school once a fortnight, and do 1-2 hrs of PE a week (2hrs on the week that they don't swim).
DS1 & 2 do an hour of football training one night a week, plus a match on Saturday. This is always outside, the pitch is floodlit so they can train when its dark.
DD does an hour of football training on a Saturday morning, she is too young to play matches yet. She also rides once a fortnight, although at the level she is at that doesn't involve that much physical exertion.
All three go to sports club for an hour one night after school, this is inside during the winter and outside the rest of the year.
They go to after school childcare which often involves physical activity, either sports outside, going to the park, or sports inside.
They also walk or cycle to school every day.
At weekends as well as football matches they spend a lot of time playing out (park, football, on their bikes etc). We usually go for a 2-3 mile walk on a Sunday afternoon, either at the local RSPB reserve, the beach or the forestry centre.
Then there is playtimes at school. Their school is very pro outside play, they have wellies and waterproofs in school and are sent out in all weathers. It isn't uncommon for them to scrap lessons on a sunny afternoon and all go out to play rounders 
So I think they get plenty of excercise, whatever the time of year!