By two measures, spring has arrived. Astronomically, spring, or the vernal equinox, occurs around March 20 each year. It is defined as when the tilt of Earth’s axis is inclined neither toward nor away from the Sun. The moment that marks the beginning of spring is when the sun is directly overhead at the equator. This year that occurred on March 20, when the maximum temperature in Madison was only 21 degrees.
Meteorologically, we can define the first day of spring as when, based on at least 30 years of observations, the probability is greater than 50 percent that should some sort of precipitation fall, it will be rain rather than snow. That date has also passed. For southern Wisconsin, that calendar day is around March 16.
Some people define spring as the first day they see a robin. We’ve seen flocks of robins in Madison this month, so that day also has passed.
While various definitions of spring indicate it has arrived, it sure seems wintry. From a climate perspective, it is not common to have this much snow on the ground after the vernal equinox. The outlook for the coming week includes below-normal temperatures.
Springtime is generally considered to be the three months of March, April and May. The official National Oceanic and Atmospheric Administration, or NOAA, outlook for spring is for warmer-than-normal weather across most of the U.S. There will have to be some warm months ahead to have that happen in Madison.
On a related note: NOAA cautions that the melting of late-season snow may cause minor to moderate flooding in the upper Mississippi River basin, including southern Wisconsin.
