Today is the first day of astronomical fall.

When you step outside, do you ever wonder why it feels like summer in June, even though the calendar says it’s spring? Or why the chill of winter lingers into March, even as the days grow longer? 

What You Need To Know

  • The seasons can be broken down by astronomical or climatological classifications

  • Astronomical seasons highlight the Earth’s position around the sun

  • Climatological seasons are aligned with our day-to-day weather and climate patterns

The answer lies in the intriguing world of seasons, where two different systems—climatological and astronomical—help us make sense of the ever-changing weather. Let’s explore these two approaches to defining seasons and why they differ.

Astronomical seasons: Nature’s cosmic calendar

Astronomical seasons are the ones most of us are familiar with, and they’re based on the Earth’s position relative to the sun. These seasons follow the solstices and equinoxes, which are key moments in the Earth’s orbit around the sun.

Spring equinox (around March 20-21): This marks the start of spring in the astronomical calendar. On this day, the Earth’s tilt is such that the day and night are nearly equal.

Summer solstice (around June 20-21): The longest day of the year marks the official beginning of summer. The Northern Hemisphere is tilted toward the sun, resulting in more daylight.

Autumn equinox (around Sept. 22-23): As we head into autumn, day and night are again roughly equal in duration.

Winter solstice (around Dec. 21-22): The shortest day of the year, this signals the start of winter. The Northern Hemisphere is tilted away from the sun, leading to shorter days.

Astronomical seasons are consistent and do not vary from year to year, making them a reliable way to track the progression of time. However, they don’t always match up with our everyday experiences of weather, which is where climatological seasons come into play.

Climatological seasons: Weather’s perspective

Climatological seasons are more closely aligned with our day-to-day experiences of weather. Instead of being based on celestial events, these seasons are defined by the typical weather patterns observed over a specific period in a particular region.

Spring: In the climatological calendar, spring encompasses March, April and May. This makes it easier to relate to the blossoming flowers and warming temperatures we associate with springtime.

Summer: June, July and August are the climatological summer months. This period captures the hottest days and summer vacations we plan.

Autumn/Fall: September, October and November represent autumn in this system. The falling leaves and cooler temperatures align more closely with our autumnal experiences.

Winter: December, January and February round out the climatological year with winter. It covers the coldest days and holiday season festivities.

Why the difference?

So, why do these two systems exist, and why don’t they sync up? The key reason is that astronomical seasons are universal, applying to the entire planet, while climatological seasons cater to regional variations in weather.

Earth’s atmosphere, oceans and landmasses all play a part in shaping local climates. For example, Southern Hemisphere countries like Australia experience their hottest temperatures in December and January, which is their climatological summer, even though it’s winter in the Northern Hemisphere.

So what “season” better lines up with my weather pattern?

This is an interesting question. And one that a little data can answer.

Brian Brettschneider, a climatologist in Alaska, put together some interesting graphs to highlight what season most represents what weather you feel. Most of the U.S. fits in with climatological summer, meaning you find your hottest temperatures between June 1 to Aug. 31.

Only a small portion of Florida and much of the west coast find their summer pattern more closely aligned with the actual astronomical summer season.

Just about everyone in North America finds winter to more closely align with climatological winter than astronomical. Meaning you’re more likely to find your coldest portion of the year between Dec. 1 and Feb. 28.

In simpler terms, astronomical seasons are like the Earth’s big-picture calendar that’s the same for everyone, while climatological seasons are like your hometown’s special weather diary, tailored to what you feel and see around you.

So, when someone tells you it’s still winter, even though the calendar claims it’s spring, it’s all about how our planet is tilting and what’s happening right outside your window.

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.