there are days for battling for place. and there are days for chasing a PR. there isn't really anything to "decide" here. it's either "on" or "not" when your event is up. good for a PR is usually a quick heat and good/fair weather. some days it's just really rainy/windy and you just battle. only silly children pout about those days not setting up for PRs. you play the ball where it lies and do your best under the conditions.
personally i think this whole discussion is silly. you run hard under whatever conditions. you fight for place every meet. but only an idiot is beating himself up for not doing his best ever in a 25 mph wind with rain.
also, depending how variable the conditions are, you could run before it rains, the rain could prove soft drizzle, it could rain then dry then rain, or it could come down all day. rather than worry about whether it's "on" for a record, how about do the professional thing and plan ahead on equipment. you know, the part you can control. bring stuff to stay dry, a jacket that sheds, some changes of clothes and shoes.
don't be a crybaby. week after or the week after that might be nice. and you still need to compete for position when it's crappy out. just don't be a silly dingus and think every week is a record setting.