My main go to crowd calendar is Undercover Tourist, it hasn't let me down to date. Other that I have found useful are Kenny the Pirate and WDW Prep School.
One key thing is to not go to a park that has Extra Mickey Hours on that day, as it means Disney guests either get in early that day or are allowed to stay later, this makes that park busier. Also check that their are no special events on that day which may mean the park closes earlier, unless you have a ticket for the event, for example, on Mickey's Not So Scary Halloween Party nights, 7pm is the cut off time if you do not have a Halloween ticket.
Below is a rough guide to how busy each month is at Walt Disney World:
January
Most of January generally has light crowds except for the first few days and when Disney has events, such as Marathon Weekend. The main problem going in January is that several rides/attractions may be undergoing refurbishment.
February
Mostly light crowds except around the half term week which can be busy, again refurbishments can be happening.
March
Early March is generally light crowds, but after that it depends when Mardi Gras and Easter fall as to how busy it is likely to be. Easter is probably one of busiest times at Walt Disney World second only to the Christmas/New Year period.
April
Usually starts off busy due to Easter and Spring Break, but at the end the crowd are relatively light.
May
Temperature are just starting to warm up and the summer crowds appear towards the end of the month, but at the beginning of the month the crowds are not too bad.
June
The summer crowds begin to kick in and it gradually gets busier throughout the month as more American schools break up.
July
Probably the busiest month it is also extremely hot - July 4th is one of the busiest days of the year.
August
The first half of the month continues where July left off, but the second half gradually gets quieter and quieter as the American Schools go back - although the temperatures are still hot, the last two weeks of August are when we go.
September
Apart from the first weekend, this is a very quiet month for crowds and if the kids didn't have school, this is when I would probably go.
October
Busier than September, but generally the crowds are not too bad.
November
This month starts with light crowds and then gets very busy during Thanksgiving week and then lightens up again.
December
Starts with light crowds for about 3 weeks and then becomes extremely busy especially from Christmas Eve onward.
One key thing is to not go to a park that has Extra Mickey Hours on that day, as it means Disney guests either get in early that day or are allowed to stay later, this makes that park busier. Also check that their are no special events on that day which may mean the park closes earlier, unless you have a ticket for the event, for example, on Mickey's Not So Scary Halloween Party nights, 7pm is the cut off time if you do not have a Halloween ticket.
Below is a rough guide to how busy each month is at Walt Disney World:
January
Most of January generally has light crowds except for the first few days and when Disney has events, such as Marathon Weekend. The main problem going in January is that several rides/attractions may be undergoing refurbishment.
February
Mostly light crowds except around the half term week which can be busy, again refurbishments can be happening.
March
Early March is generally light crowds, but after that it depends when Mardi Gras and Easter fall as to how busy it is likely to be. Easter is probably one of busiest times at Walt Disney World second only to the Christmas/New Year period.
April
Usually starts off busy due to Easter and Spring Break, but at the end the crowd are relatively light.
May
Temperature are just starting to warm up and the summer crowds appear towards the end of the month, but at the beginning of the month the crowds are not too bad.
June
The summer crowds begin to kick in and it gradually gets busier throughout the month as more American schools break up.
July
Probably the busiest month it is also extremely hot - July 4th is one of the busiest days of the year.
August
The first half of the month continues where July left off, but the second half gradually gets quieter and quieter as the American Schools go back - although the temperatures are still hot, the last two weeks of August are when we go.
September
Apart from the first weekend, this is a very quiet month for crowds and if the kids didn't have school, this is when I would probably go.
October
Busier than September, but generally the crowds are not too bad.
November
This month starts with light crowds and then gets very busy during Thanksgiving week and then lightens up again.
December
Starts with light crowds for about 3 weeks and then becomes extremely busy especially from Christmas Eve onward.