What happens if its dry when all the cars head out on their out lap on dry tyres, then when they are lined on the grid, or on the parade lap it starts to rain heavily? Are the cars allowed to pit on the parade lap for wet tyres or do they have to start a wet race on dry tyres and come in on their first lap?
tbh, if it started to rain during the parade lap it would depend entirley on how heavy the rain is, most of the drivers would ignore it, unless an absolute torrent camde down, which if heavy enough might even reult in a red flag.
On the parade lap, if it rains the race proceeds as normal, but everyone is free to pit for wet tyres and start in the pit lane if they wish. Should they do so, it becomes a scramble for the pit exit because the starting order would be single file in order of arrival at pit exit.