A historically intense April cold snap has descended on Europe, with temperatures plummeting to 20 to 30 degrees below normal. The record-breaking cold has triggered harsh frosts, shocking early-blooming plants and crops in several countries. "If those flower buds get hit by frost, they don't regenerate that spring, and they don't regenerate for the whole year," said Theresa Crimmins, the director of the USA National Phenology Network and a research professor at the University of Arizona.