I am supposing you are meaning humid climate as in Carolinas and Georgia in US and Central and Southern China ie. on East coast of a large continent. This would actually be more like 1800 miles from the nearest very cold areas (Northern hemisphere). The same latitude on West coast of large continents seems to produce deserts - Baja California and Morrocco for instance. Something to do with the Earths axis and which way it spins, plus ocean currents and wind. Trying to sound like i know what i am talking about here!
I suppose you could have compressed distances between your worlds climate zones - moon / sun effects on weather etc? As long as you keep a gradual change between climate zones you can keep it realistic. Our world is a great template to go by, but some variation for your fantasy one wont look wrong.