I agree with urbanknight (there are many factors that can lead to hot spots, shoe fit being a big one, especially tightness in the toebox, instep and forefoot areas) and AlgarveCycling (some fit issues can be helped with a good quality footbed, most of the ones sold with cycling shoes are minimal at best - I am convinced that Sidi fully intends their footbeds to be replaced with a footbed that works for the purchaser).

Also, hot weather can make hotspots appear earlier in the ride, and can make them worse. My feet can swell during a hot ride, especially later in the day when the pavement heats up and you get heat radiating from the road affecting your feet. Pay attention during a hot ride and loosen shoe straps/buckles before your hotspots start.