4.5 months of this year, National Weather recorded 1,200 cases of tornadoes, while the average for the year of 1500 is observed. Scientists do not see this phenomenon and say that there is a natural inter-annual variability, which does not alter the general trend of horizontal. The reasons for a spike notes several factors — from the natural to the social. This year has been very mature La Niña. It was the result of a cold and snowy winter. In spring, when the south began an intensive warm up, north of the continent was still cold. This has generated significant temperature contrasts and, as a consequence, to the emergence of active weather systems. Furthermore, due to the La Niña experienced strong westerly flow. Wet and cool air masses from the Pacific Ocean brings rain not only on the U.S. West Coast, but also penetrated inland. Additional moisture caused severe thunderstorms and tornadoes. Social factor revealed in extended surveillance. Tornado — a small-scale phenomenon. In a sparsely populated area, they go unnoticed. Now actively colonized previously uninhabited areas. There was a population — there were tornadoes. Meteorologist Greg Carbin said on this occasion: "Just because we're seeing more tornadoes, we should not conclude that there are more tornadoes."