If you have to implement a rain plan, I still recommend having at least two distinct places for your three wedding day events. You can double up the reception space with either the ceremony or the cocktail hour, but it is generally not comfortable to do all three under the same roof.
A tent to cover a rainy ceremony doesn’t have to be all that large, as guests will either be standing or seated theater-style. Another option is to hold your ceremony in the reception tent, with guests witnessing your vows on the dance floor, like in the photo above.
If you have hired live musicians for your wedding, they will require that they be in a safe and dry spot during their performance to protect their equipment. Even if you intend to let your guests weather a slight drizzle during your ceremony or cocktail reception, you need to make sure there is somewhere the musicians can stay completely dry and still be heard.
The cocktail reception location may be the toughest to cover with a tent. Luckily, the dance floor of your dinner tent makes a perfect backup location. That is, unless the dance floor was used for your ceremony, in which case you need to find an alternate location for the cocktail reception. If I had to make a broad generalization, I recommend getting a tent for your ceremony and moving the cocktail reception to the dance floor in your reception tent.
In the event of rainy weather, you will likely want sidewalls on your tents. They will keep the rain and cool air out and keep the warm air in, allowing your guests and your equipment (who wants to sit on a wet chair for 3 hours?) to stay dry and comfortable. If rain is possible, but not imminent, you may consider putting up a few precautionary pieces of sidewall in order to protect crucial items under the tents, such as the band or DJ equipment, the bar, and the cake table.
If it is going to rain, you will also want to consider getting marquee tents to link the different areas of your event together, including the location where your guests arrive and depart, the restroom, and the caterers’ prep area. You don’t want your guests (or the staff carrying your food) to get rained on, plain and simple. Proximity between these areas is especially important if the weather is poor, because more marquee tents means more money. The closer every space is to the other, the easier the rain plan will be on the budget.
Implementing a rain plan may also mean revisiting the parking situation. If you had planned for guests to park on grass, that plan may require amending. If you planned on guests walking from an off-site parking lot, you may want to instead offer a shuttle. If you aren’t using any shuttle buses, hiring a valet service is probably the best way to handle your guests’ parking situation in the rain.