Europe has about 300 tornadoes per year – much more than estimated by Alfred Wegener in his classic book "Wind- und Wasserhosen in Europa" ("Tornadoes and Waterspouts in Europe"). They are most common in June–August, especially in the inlands – rarest in January–March. Strong and violent tornadoes (F3–F5) do occur, especially in some of the interior areas and in the south – but are not as common as in parts of the US. As in the US, tornadoes are far from evenly distributed. Europe has some small "tornado alleys" – probably because of frontal collisions as in the south and east of England, but also because Europe is partitioned by mountain ranges like the Alps. Parts of Styria (Steiermark) in Austria may be such a tornado alley, and this county has had at least three F3 tornadoes since 1900. F3 and perhaps one F4 tornado have occurred as far north as Finland.