With the weather the way it is here in Chicago, it’s all based on Temperature not the specific month. As long as air temperatures and surface temperatures stay at or above 50 degrees your painting project will be a successful one. Some newer products can be safely used down to 35 degrees.
The other thing to take into consideration is day and night temps. If the night time temps are much cooler than the day time, there may be condensation on the areas you need to paint as they warm up. This happens more in the fall. If it’s really hot out, then painters need to try and follow the sun. Stay on the shady side.
Rain. There is nothing you can do here. Just make sure your paint is dry before it rains and make sure your project is dry before you paint.