Hi Geoff! Welcome to the Guild!
Have a look at Fractal Terrains, which generates climate / temp / altitude maps automatically. Here is an example which took about about 10 seconds to create because the map is randomly generated. If you want to create your own continents it'll take longer, but the rainfall / climate conversions are still done by the software. (I have no idea how accurate they are, but there are lots of settings you can play with - axial tilt etc, so I guess they are based on some sort of science).