Some of the past summers have not been the most spectacular. There has been reports of floods, in my bike trip across Europe last year for the most part was marred with rain and other poor weather. This is often a problem when travelling to some parts of the world, especially in temperature climates.
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This does require you to alter your travel plans somewhat. In some part of the world you are just going to get wet. Although that does put a dampener on things that is about as far as it goes. But in some parts of the word this could be decidedly worse.
For example some parts of Asia the wet season is more extensive, and this can make whole areas impassable. Of course the weather can have the opposite effect too. Being dehydrated is much worse in the warmer parts of the world such as the middle east and Australia in the warmest parts of the year.
No matter where you are it is always wise to prepare for the worst. Weather isn't just getting wetter but more extreme. So this doesn't just mean the summers will get hotter and wetter but winters will be colder too. So its important that you do your research and pack accordingly. If its somewhere more exotic or further away then that is going to be even more important.