Hi Dayna! April is one of my favorite months to visit Disney World -- in my experience, the weather is usually beautiful then! The high temperatures generally hover around 80 and the lows around 60. Although April showers bring May flowers in much of the United States, April is historically the least rainy month at Disney World.
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Frequently Asked Questions page on the Disney website states that park attendance levels are at their highest from mid-March to late-April since that period usually coincides with Spring Breaks at schools and colleges. However, the Easter holiday is unusually late this year, which may affect the crowd levels in early April. I like to check the Crowd Calendar on the unofficial site touringplans.com, which predicts attendance levels based on many factors including past history, Extra Magic Hours, and holidays. According to this site, crowds will be high in mid-March and late-April, but only at moderate levels during the first week of April. I've found that the Crowd Calendar is generally quite accurate, so it looks like you timed your trip perfectly!
Hope you have a magical visit! Come see us again at the Moms Panel if you have more questions! We're happy to help!