Here in Arizona's mild winters even regular fluorescents tubes flicker
in my garage.

...Jim Thompson


They're probably those crappy 34W energy saver tubes with magnetic
ballasts that usually don't drive them harder than about 25W. Those were
a hack from the 70s energy crisis and hardly work in a drafty room
indoors. Try some electronic ballasts driving T8 tubes, they work fine
in the near freezing temperatures in my unheated garage in the dead of
winter. As an added bonus they're 32W and brighter than most of the old
40W tubes and the high frequency operation pretty well eliminates
strobing with rotating machinery.