Location
Derechos in North America form predominantly from May to August, peaking in frequency during the latter part of June into July. During this time of year, derechos are mostly found in the Midwestern United States most commonly from Oklahoma and across the Ohio Valley. During mid-summer when a hot and muggy airmass covers the north-central U.S., they will often develop farther north into Manitoba or Northwestern Ontario, sometimes well north of the U.S.-Canadian border. North Dakota, Minnesota and upper Michigan are also vulnerable to derecho storms when such conditions are in place. They often occur along stationary fronts on the northern periphery of where the most intense heat and humidity bubble exists. Late-year derechos are normally confined to Texas and the Deep South, although a late-summer derecho struck upper parts of the New York State area after midnight on 7 September 1998. Warm season derechoes have greater instability than their cold season counterpart, while cool season derechoes have greater shear than their warm season counterpart.
Although these storms most commonly occur in North America, derechos can occur elsewhere in the world, although infrequently. Outside North America, they sometimes are called by different names. For example, in Bangladesh and adjacent portions of India, a type of storm known as a "Nor'wester" may be a progressive derecho. One such event occurred on 10 July 2002 in Germany: a serial derecho killed eight people and injured 39 near Berlin. They have occurred in Argentina and South Africa as well, and on rarer occasions, close to or north of the 60th parallel north in northern Canada. Primarily a mid-latitudes phenomenon, derechos do occur in the Amazon Basin of Brazil. On 8 August 2010, a derecho struck Estonia and tore off the tower of Väike-Maarja Church.
Read more about this topic: Derecho