Option 1: Reschedule
It's always an option — and if you have a specific look you're going for, it may be the best plan! As fun as rainy sessions may be, the reality is that they are never going to have the same look as a day with sun.
Option 2: Move Things Indoors
In-home or studio sessions have a magic of their own, and a cozy rainy-day session indoors can be pretty magical! This is a great option if you're not a fan of getting wet, but don't want to push your photo session date back.
Option 3: Head up the Mountain (and pray for snow!)
Works best if you live near mountains. Also if it's almost winter.
Option 4: Risk it/Embrace it
I have a trusty clear umbrella that I always bring if there's a chance of rain. Not to mention, the VERY best sunsets are always right after it's rained. It doesn't always clear up, sometimes it's just wet and we play with that. But sometimes, if you're lucky, it will clear up and we will get gorgeous skies (and maybe even a rainbow!)
