[mywittyname]

The associated study claims that these stones have been seen many times - they are likely to appear about five times per century. The study points out that the causes of droughts have changed. Previous droughts were largely due to a lack of precipitation. The current levels of precipitation is actually as high as it has even been.

The cause of the current drought is record levels of heat. Despite statistically high levels of rain fall, the temperature of the region is so high that the rivers are drying up anyway.

[pydook]

Not entirely true, at least locally. Precipitation in Czech republic in August is just 40% of normal state for this month [1]. The lack of rains is a big deal here.

[1]: Report about draught from Czech meteorological agency, http://www.chmi.cz/files/portal/docs/tiskove_zpravy/2018/TZ_...

[pydook]

Edit: wrong link, correct one is http://portal.chmi.cz/files/portal/docs/tiskove_zpravy/2018/...

[mywittyname]

I was summarizing the source document for this article, which is actually a few years old at present.