As March rolls around every year, so does meteorological spring. Jump ahead a few weeks and suddenly astronomical spring begins.  

So, what is the difference? Simply put, astronomical spring relates to the position of the earth in relation to the sun, while meteorological spring relates to the warming temperatures from March through May. For meteorologists and climatologists, spring begins March 1. Below, we will define why that is and how it may be more accurate to represent the seasons.  

People have observed seasonal changes around them (temperatures, color of leaves, animal migrations, etc.) for thousands of years. The natural rotation of the earth around the sun each year forms the basis of the astronomical calendar.  

Seasons are defined by Earth’s tilt and the sun’s alignment over the equator. During the vernal equinox, the Earth passes directly over the equator. After the equinox, the northern hemisphere will see more daylight than darkness until the summer solstice.  

Because earth’s travel around the sun takes 365.24 days, an extra day is needed every fourth year, called a Leap Year. This extra day causes the exact day of the equinoxes and solstices to vary. In addition, the elliptical orbit of the earth results in different lengths of astronomical seasons.  

These changes make it difficult to achieve consistent data collection and compare seasons from one year to the next. Because of this, meteorological seasons came to be.

Meteorological seasons are split into three-month groups based on the annual temperature cycle and the calendar. Winter includes the coldest months of the year and summer has the warmest months.  

Both spring and fall are transitional, where temperatures are rising (spring) or falling (fall). Meteorological observing and forecasting led to the creation of these seasons, and they are more tied to the monthly calendar we all use today than the astronomical seasons.  

The consistency of the three-month seasons allows meteorologists and climatologists to more easily calculate seasonal statistics. This, along with monthly statistics, is very helpful for agriculture and commerce throughout the year.  

Overall, meteorological seasons provide a simple, more common-sense way to describe temperature changes over the course of the year.

Our team of meteorologists dives deep into the science of weather and breaks down timely weather data and information. To view more weather and climate stories, check out our weather blogs section.