Two years ago, on August 31, 2014, Malmö was flooded. The picture at left is from Malmö. Passengers on a bus caught in the flood leave the bus on a ladder. Malmö is a quite flat city on the coast of Öresund, and much of the city was actually flooded. In the condominium house where I live, we had water in the basement, and extensive repairs have been made. But many people were hit much worse than us. (No one was killed or severely hurt, though.)
Exactly two years later, we had the kind of temperature contrasts in Europe that you can see in the image at right. I think it is these temperature contrasts that cause the extreme weather conditions that my city has experienced a few times in later years. I think it has to do with global warming, because we certainly didn't have any flooding in Malmö between 1964 and, say, 2010 or so. This picture
is from a winter storm in December 2012. The central, downtown part of Malmö so nearly got flooded.
It is practically impossible to relate a handful of extreme weather events in a single location, to global warming. One must look at many locations over a sufficient period of time and analyze the data against older records. The probability of extreme rainfall/flood events like these in any one location is typically measured in long time scales like 1 in 10 years, 1 in 50 years, 1 in 100 years, etc. Of course, extreme rainfall events occur somewhere on the surface of Earth at all times. And at any single location, it is not uncommon to observe clusters of extreme rainfall events in a relatively short period. Such is probability.
However, it is quite certain that flat coastal cities and towns can expect an increased probability of flooding in the coming centuries, if the sea continues to rise to predicted levels. Extreme rainfall events concurrent with higher
high tides and/or storm surges, pose an expensive problem for such populations.
In general terms, increased urbanization also increases the risk of flooding, unless the urbanization is designed and built well (and typically at extra expense), to account for the increase in runoff from paved surfaces.
Global warming is quite likely to change average monthly precipitation in locations all over the world. It will likely also change the probabilities of average rainfall intensities within individual storm events, which is the factor of primary importance to those interested in flood mitigation. But how much these values change (up or down) due to global warming, is not at all well understood at this point in time.