The shutdown is a three week holiday for the workers on the assembly line. During this time they'll do any work that needs to be done in the factory, such as retooling and giving tired robots a break.
Why would they be busy "before September"? What's so special about this time? They're busy all year round, but the guys on the line do need a break.
More new car orders are placed around spring time as people want to take delivery in summer (and with new plates in UK case). So it does seem odd to shutdown now in this sense. However, the workers don't want to have holiday in winter so they couldn't very well stop then.
That said, its not a *full* shutdown. They're trying to keep production running, I guess at some reduced level but how reduced it is impossible to say.
EDIT:
Nice table MH. Why no one has thought to do that before I don't know, we're forever discussing what BW means what your idea of a table answers those questions! Could add a column for date week commencing too for those who don't have the week numbers in their calenders.
That said, its not a *full* shutdown. They're trying to keep production running, I guess at some reduced level but how reduced it is impossible to say.