One question I get asked over and over is "Do you keep your flowers in a cooler". The short answer is no, except on rare occasions.
The long answer is this. I've worked in the the wedding industry doing events for 8 years. I've always been a boutique business, meaning that I only do one or two events per weekend. We always get our flowers late in the week, and use them for events just days later. This helps ensure they are the freshest they can possibly be. I never needed a cooler because we kept flowers on hand for a minimal amount of time.
Many floral designers do use coolers. Why? Because they do lots of events, and not just weddings. Traditional designers get flowers early in the week and design and create with those blooms all week long. They need coolers to help prolong the life of the flowers for as long as possible. Much like produce or food in the fridge, the cold helps keep things fresher, longer. However floral coolers are specially designed for flowers, to keep them at an optimal temperature and humidity for best freshness.
Sometimes in blog posts I will recommend that people put their flowers in the fridge overnight. I do this when a project calls for flowers to be out of water, for example when making a floral crown, or for this framed flowers project. On these occasions, when blooms won't be in water, it's absolutely necessary to keep them in a fridge if you want to do them ahead of time (I wouldn't recommend anything longer than the night before an event).
It should be noted, however, that fridges meant for food are not optimal for flowers, but in a pinch, they can work. What I always recommend is people do a Fridge Test. This is so you can see if your fridge is a good temperature for flowers. I'd recommend doing this test ahead of time, and not the night before your event, or you may end up with a pile of mushy, un-usable blooms.
Take a flower, out of water, and place it in your fridge overnight. If you check it the next morning and it's still fresh then you can feel pretty comfortable putting your floral projects in your fridge. However if your flower feels a little soft, or even mushy, or the petals are browning at the edge, your fridge is probably either too cold, or too warm, and I wouldn't recommend using it to keep flower fresh.
Ideal temperature for flowers is 34-36 degrees Fahrenheit, with 90% humidity. Some fridges will let you adjust the temperature settings, but you'll still want to test them just to be sure. Also keep in mind that fruits and veggies give off ethylene gas and speed the wilting of flowers, so if it's best to not have your fridge packed with fruits and veggies when you're trying to preserve flowers.