A state of emergency has been declared in Boznia-Herzegovina after torrential rain and flooding.

It's one of several European countries being affected by extreme weather, either floods, droughts, heatwaves, or sometimes all three.

In Italy, floods are the worst for a century causing death, injury and destruction. The northern province of Emilia-Romagna is the worst affected region at present with upwards of 20,000 homes and businesses flooded.

The inundations come after a prolonged period of drought that has affected much of southern Europe including parts of Spain and Portugal.

This means the earth has turned dry and hard so when heavy rain falls, rather than being absorbed, the water runs off and causes flash floods.

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According to the Hungarian Meteorological Service's climate expert, Olivér Szentes, these extreme events alone are not necessarily the results of climate change, but they could be.

"We talk about climate change when the distribution of something changes," he explained. "But it is a long-term process. If we pick a period of heavy rainfall or a period of dry weather, that's not climate change. If certain phenomena become more frequent on a sustained basis, then we can talk about climate change."

By way of example, there has been a lot of rain in the Hungarian capital Budapest recently, but the situation is not described as extreme - such downpours are normal.

However many climate observers point to the increasing frequency of heatwaves, droughts and flooding that they claim is a result of climate change.