timing for starting a new hive

What conditions are optimum for a successful start with a new hive? Appreciating that bees live in a variety of climates and assuming we have a choice, is there a 'best' temperature, humidity, or other weather conditions that will ensure a favorable outcome?
Thanks!

Bees keep their cluster at about 95 degrees, so I would try for as close to that as possible. You wouldn't want to start them in the rain because too much moisture can cause mold issues inside the hive. It's probably easier for the bees to add moisture than it is to take it away. Try to make sure there are plenty of flowers around or you will have to feed them sugar.
Anytime is better than no time. A couple years I waited too long and had to do without.