We have been to Disney at various times and this is what we experienced:
January (2nd week) - low crowds, but cold
January (last week) - low crowds, but cold
Feb. (first week) - low crowds, still cold
Feb. (2nd week) - good size lines, cool
March (mid) - good size lines, nice & warm
April (2nd week)- good size lines, nice & warm
April (3rd week) - huge crowds, nice & warm
April (last week) - mid-low crowds, nice & warm
Sept (2nd week)- ultra low crowds, hot & humid
Sept (last week) - low crowds, very warm (food & wine festival, busy)
Oct. (first week) - low crowds, very warm (food & wine festival, busy)
Nov (mid) - low crowds, a little chilly
Low crowds- 0-15 min wait
Good size lines- 15-20 min wait
Huge crowds - 30-60 min wait
warm- sun shining, enjoyable
hot & humid- very hot, sweating while standing in line doing nothing!
very warm- hot, sweating while moving around...
This is just what we experienced while we were there.. Others may have different experiences.