Severe Cold Winters in East Asia Linked to First Winter of La Niña Events and in North America Linked to Second Winter

La Niña often persists for two years, unlike El Niño. Five single‐year and 8 multi‐year La Niña events occurred over 71 boreal winters (1950/51–2020/21). Atmospheric reanalysis data show a marked increase in diabatic heating over the tropical northwestern Pacific (TNWP) in first winters of La Niña events in addition to a decrease in diabatic heating over the tropical eastern Pacific, common to first and second winters. Linear baroclinic model experiments indicate that combinations of the heating form different atmospheric teleconnections in the mid‐latitudes; first winters with the increased heating over the TNWP form teleconnection across the North Pacific, leading to cold winters in Japan. In second winters with the reduced heating over the TNWP (∼50% of first winters), teleconnection shifts east, resulting in severe cold winters in northwestern North America, whereas there is no impact on Japan. Plain Language Summary La Niña is the negative phase of the El Niño–Southern Oscillation cycle, typically characterized by a zonal dipole structure with surface ocean cooling in the tropical central Pacific and warming in the tropical northwestern Pacific (TNWP) in boreal winter. La Niña has been regarded as a mirror image of El Niño, and the impact on climate has often been considered as such. However, recent studies have reported that La Niña, unlike El Niño, can last for two years. Five single‐year and 8 multi‐year La Niña events occurred over 71 boreal winters from 1950/51 to 2020/21. Marked difference between first and second winters of La Niña events is atmospheric heating over the TNWP, resulting in different effects on the world's climate. In first winters, heating over the TNWP leads to surface air cooling of ∼0.38 K in Japan, whereas second winters with reduced heating over the TNWP have a pronounced effect on the eastern North Pacific, resulting in cooling of ∼1.7 K around Alaska. Our results indicate the importance of predicting not only the occurrence of La Niña but also its persistence, which is especially important for the living of North America. Key Points Diabatic heating related to surface warming over the tropical northwestern Pacific is noticeable in the first winter of La Niña events First winters of La Niña events bring severe cold winters to East Asia, with surface cooling of ∼0.38 K over the 3‐month mean in Japan Second winters of La Niña events cause severe cold winters in northwestern North America, with a cooling of ∼1.7 K around Alas