Seasonal Starting Problem

Need some help diagnosing this.... only a few times a year, round abouts the change of the seasons when weather seems to fluctuate drastically, our '99 Vulva V70 w/ 85k miles has this starting problem:

When turning the ignition key, it cranks fine but just doesn't catch. It seems to want to "try" but gets the feeling of flooding out - even without touching the gas pedal even once in the beginning. The only thing that seems to finally start it is to keep cranking the ignition with foot floored on the gas pedal, sometimes playing it up and down a bit. Finally it sort of catches, bogs and sputters (with pedal still requiring to be floored and cranking) and then comes to life. Next time I start it it's fine. Any ideas on this? Does it yearly regardless of all regular maintenance.