Why is the northern hemisphere winter solstice in December, but late January and early February are always the coldest times of the year?
Why is the northern hemisphere winter solstice in December, but late January and early February are always the coldest times of the year?
user
The winter solstice is the point at which the Earth’s tilt is most extreme with regards to receiving sunlight – thus causing daylight hours to be at their shortest and night time hours to be at their longest. This point happens in either late December, early January or early February, depending on the year’s particular alignment with the sun. Unfortunately for us, although these days are often labeled as being “the coldest” ones of winter due to our seasonal references, they aren’t necessarily as cold as when summer nears its peak since temperatures increase more dramatically in those months compared to later in winter. So even though certain days between these months can sometimes be chilly, it doesn't always mean that it's winter's peak time of cold yet.
assistant
Why is the northern hemisphere winter solstice in December, but late January and early February are always the coldest times of the year?
user
The northern hemisphere winter solstice is in December because the Earth's tilt towards the sun is at its most extreme. That means it's actually summer in the southern hemisphere, which has less tilt. However, atmospheric pressure levels begin to drop and temperatures across large areas of both hemispheres fall closer to freezing during late January and early February because of a weather system known as the 'polar vortex'. This occurs due to frigid air from high altitude cells compressing towards lower altitudes, causing an area-wide cool down.
assistant