Koreans went from wearing short sleeves to pulling out padded winter jackets last month as temperatures swung dramatically between summer-like heat and early winter chills. The reason, meteorologists say, was a massive high-pressure system thousands of kilometers away over Russia's Ural Mountains. The atmospheric phenomenon, known as "Ural blocking," disrupted the usual flow of weather systems, allowing cold Arctic air to surge south toward the Korean Peninsula. Scientists say rapid warming in the Arctic may have helped intensify the disruption by weakening the jet stream that normally helps contain frigid air in northern latitudes. The Korea Meteorological Administration (KMA) released its analysis of October's climate conditions on Wednesday, identifying extreme temperature variability as the month's defining characteristic. The difference between the warmest and coldest daily average temperatures nationwide reached 14 degrees Celsius, the fourth-largest October fluctuation on record. The average temperature stood at 22.1 degrees on Oct. 12 before plunging to 8.1 degrees on Oct. 28. Se