Winter in North America Is Cold — Dec. 2017-Jan. 2018

Geert Jan van Oldenborgh, Hylke de Vries (KNMI), Gabriel Vecchi (Princeton University), Friederike Otto (University of Oxford), Claudia Tebaldi (Climate Central and NCAR)

World Weather Attribution

The two-week cold outbreak in the northeastern U.S. and southeastern Canada was highly unusual in the current climate; however, it is not unprecedented.
Cold waves like this have decreased in intensity and frequency over the last century, but still occur.
Temperatures like these are now about fifteen times rarer. This is equivalent to cold waves being about 4ºF (2ºC) warmer than they used to be.