A January Thaw occurs when a surge of warm air brings several days of above-freezing temperatures in midwinter, briefly melting snow and ice. Most common in the second half of January, thaws are especially noticeable in the central and eastern U.S. These warm spells can feel like a “false spring,” easing cold stress and energy use. However, they are temporary, and colder air usually follows, allowing melted snow to refreeze and create slippery conditions.