Ok so a thunderstorm isn't ideal, but I'll bet it won't last all day and the skies before or just after would make incredible photographs. Your photographer will be in the know and watching out for the 'light' the just right moment, so please, if you take anything away from this it's to trust them!
I guess that was TIP 1, so TIP 2... if it looks like rain, invest in a clear brolly, or ask your tog if they're bringing one along. Newlywed couple's photos huddled together under an umbrella whilst rain pours all around them, yes please, this is giving me actual goosebumps!
TIP 3. Provide some shade. Or wait until a better time of the day for groups and couples portraits outdoors, if you happen to have a gloriously sunny day, in the middle of Summer, avoid the important photos during the midday sun, there's not much worse than avoiding shadows, squints and asking your friends and family to please take off their hats and shades.
TIP 4. Following on from TIP 3, the best times of the day... golden hour allll the way for couples portraits! or Blue hour- incredibly beautiful, soft light, and underrated (the hour after sunset). If you are starting to plan out the timings of your day I strongly suggest ensuring you have booked your photographer and are consulting them in your plans, they'll be able to advise on how long to put aside for each portion of the photographs and when your best time of the day is likely to be for your outdoor photos. Night-time is pretty spectacular too, with a nice back light!
TIP 5. If there is no hope of outdoor photos (and we are talking hurricane weather here) find a quiet spot away from your guests, or even better, let your photographer scout out a spot, near a beautiful window for some time alone together to take it all in (with your photographer capturing all those sweet moments obviously- we're pretty discreet)!
And lastly, apart from maybe grabbing a blanket to wrap around you between shots (or during) get out in that freezing winter weather, my last wedding was in January and a freezing fog descended and didn't lift all day. This however, made for some epic photographs, atmospheric and unforgettable.
Whatever the weather, your photographer will work with you to make the best of it!