Summer is not WDW's busy season. I define it - to some extent - using WDW's own pricing seasons.
August is the least expensive time of year to visit WDW. Here are some AKL Monday night rates for a standard view room:
Easter - peak = $708/night
What WDW calls "regular" season (for example 4/6-4/23): $580
Memorial Day: $680
"Summer" (5/27-7/4): $558
"Summer 2" (7/7-8/15): $539
"Value 2" (8/16-8/29, 9/2-9/12): $496
Much of summer (August and September) is specifically called VALUE season, which is Disneyspeak for the lowest price offered all year. (Technically, the January value season was $9 less/night than August.)
In addition to the already relatively low summer prices, starting tomorrow WDW will release a Free Dining promotion that covers all of July and 9/1-9/7 (Disney Visa). This is Disney's third attempt at offering free dining promo for this summer: onsite guests have been offered Bounceback promos, and WDW offered a free dining promo earlier this year that covered most of this upcoming summer. Odds are high they will also release a summer AP rate.
Additionally, WDW discounts the price of park tickets in the summer.
This week- not peak pricing- a 7 day base adult (per UT website) costs:$752
June 18: $685
July 16: $690
August 19: $553
Dec 10: $743
Dec 24: $805
The highest summer tickets are the two weeks around July4: 6/25=$743, 7/2: $749, then 7/7 the price goes down to $707.
Many people this summer will be buying the Magic 4-day discounted ticket though instead of a full week at WDW.
If you read anything WDW related, then you already know WDW's summer temps are often described as "hotter than the sun, " and "expect to be dripping in sweat." People get scared off by statements like that.