By Climate Central
Astronomical spring, marked by the vernal equinox, begins at 6:29 a.m. (10:29 GMT) on Monday, March 20. This is the date when the amount of daylight is equal to the amount of night across all parts of the globe. The term “equinox” comes from the Latin, meaning “equal night.”
Warm spring days in these U.S. cities
Spring is getting warmer, on average, as the globe heats up from the increase in greenhouse gases in the atmosphere. As a result, the number of spring days with above-normal temperatures is increasing in many places in the U.S. In an unchanging climate, the number of days above normal and below normal should be relatively balanced and constant through the years. For meteorological spring, that number would be 46 out of the 92 days. In the majority of these cites, the number of days above normal has risen sharply. In some cases, there are more than 10 additional above-normal days than there were a few decades ago.
As the spring warms and begins earlier, the pollen season is lengthening, increasing the risk from allergy-induced respiratory diseases, like asthma. The warm spring also allows plants to bloom before pollinators have migrated in for the season, which can affect agriculture ranging from family farms to backyard gardens.
Methodology: The graph indicates the number of spring days above the 1981-2010 NOAA/NCEI climate normal. For each month, we counted the number of days when the daily average temperature departure from normal is greater than zero. The months of March, April, and May (meteorological spring) were analyzed.