When is it a good time to do out door house painting?

Now or in the fall before it gets really hot out.

Most outdoor paint cans have a minimum temperature listed. You can probably even find the info on your favourite paint's website.

Pick a day soon, when the night temp doesn't fall below the minimum recommended temperature.

Do not paint in direct sun if you can help it. So start on the side that isn't and work your way around.

Also try to pick a day when rain isn't forecasted for a few days. This may seem obvious, but I painted during humid weather, and 1.5-2 days later it rained and washed off some of the boards, and "pitted" others.

paint in dry weather. Low humidity will get the paint dry appropriately. High humidity the paint may not dry and remain sticky. If you are doing the painting yourself, there are pre made kits for painting the trim, it’s a paint pad system. not a brush. The pads are equipped with a place to add a long handle like a broom handle, i was able to paint the facia with it, me standing on the ground. The smaller pads do the the window trim. They clean up quickly.

Spring.

Late spring or early fall (at least in Oregon).

After rain has stopped, but you outdoor temperature is fairly constant at about 70 or so.