Prepare all your painting materials as you wait for a break in the rain. Keep your painting materials gathered in your garage or spare room. Make a check list of materials you will need, and check the list multiple times to ensure that you have everything you need. Purchase painting materials that are meant to make your painting job faster and easier -- like a power paint sprayer.
Purchase more paint than you estimate you'll actually need. When it's finally dry enough to paint your house, assume you're going to want to get the job done as quickly as possible, before it starts to rain again. This means you won't waste time on extra trips to the paint store for more materials.
Gather a squadron of family and friends to help you complete the painting project as quickly as possible when the work finally begins. Hire contractors if necessary. Remember that for every extra person you'll need additional materials, like extra ladders, paintbrushes and paint rollers. Check weather reports frequently and contact your helpers with regular updates, to inform them when you hope to do the painting project.
Give all your helpers a role in the painting process, and make sure that everyone knows what to do. Efficiency is key. When there's a break in the rain, whether for a day or two days, the entire job must be done as quickly as possible in order to give the paint adequate time to dry.
You won't be able to paint with oils under these conditions. Choose your latex paint very carefully -- read the cans of paint for acceptable moisture and temperature conditions during the painting process. Look for durable, mildew-resistant paint types, and most important, check the amount of time that the paint needs to dry before it can get wet. This will likely be at least four hours, so plan accordingly.
You'll want at least three relatively dry days for the house painting process -- one day drying time after the rain ends, one day of painting time and one day of curing. Choose a three-day span when the weather report predicts a 40 percent or less chance of rain. If you can possibly put off your house painting project to a dryer period of time, you should do so. House painting is an expensive, labor intensive project that you don't want to do twice.
Don't attempt to paint a house under these conditions if this is your first time painting an exterior -- wait for better weather if you don't know what you're doing. Limit this project to a smaller, single story house. A larger house will take too long, and may have too many unforeseen, complicating factors. Finally, there may be some blistering in the paint, so budget for potential repairs later in the year.