Increased temperature variance adds to the probability of extreme high temperature events over and above what could be expected simply from increases in the mean alone. (ipcc.ch)
It's not flooding or other weather disasters that cause people to move but rather extreme high temperatures, at least in Pakistan (scientificamerican.com)
North Dakota, South Dakota and Montana Drought: $ 2.5 Billion When: March 1 to Dec. 31, 2017 Deaths: 0 The damage: A «flash drought» characterized by extreme high temperatures and little rainfall hit North and South Dakota and Montana beginning in March. (scientificamerican.com)