At the time of this writing, we’re approaching to the period when we experience scorching hot days in the Northern Hemisphere, when many are heading to the beach to have fun or some who stay indoors, irritated with the intense heat and chilling inside their air-conditioned rooms. We generally call this as the “summer season”. However, the proper interpretation of the season we’re in varies from where you are Earth. Specifically, only 2 (dry and wet) in the tropical regions and 4 (winter, spring, summer, autumn/fall) in the temperate regions.
The term “season” can be described in two classifications; meteorological and astronomical. The meteorological season primarily elaborates on the temperature variations being observed over a certain area. For example, here in the United Arab Emirates, when meteorologists found a consistent trend of high temperature measurements for couple of days, they can conclude that is the (warm and) dry season. On the other hand, the astronomical season depends on the corresponding orientation of the Earth’s axial tilt with respect to the sun at specified positions of its elliptical orbit .
The Northern and Southern Hemispheres have opposite seasons because of the different orientations of the Earth’s axial tilt with respect to the Sun (see figure below). Particularly, when the Northern Hemisphere is tilted towards (away) the Sun, notice that it receives more (less) sunlight than the Southern Hemisphere. This means it’s summer (winter) in the Northern Hemisphere and the inverse in the Southern Hemisphere.
Figure 1. The orientation of the seasons in both hemispheres 
This article will only focus on determining a definite season by astronomical means. It involves knowing the prominent constellations (the celestial boundaries) and asterisms (the imaginary patterns/figures created from “connecting the stars”) crossing the meridian (see image) in the night sky in a particular time of year, concentrating on summer and winter seasons.
Figure 2. The Celestial Meridian, an imaginary half-circle crossing the celestial poles and the zenith in the celestial sphere (Image credit: Centre for Astrophysics and Supercomputing)
I. The Winter Sky
Figure 3. The Winter Sky (Image Credit: Stellarium)
The prominent winter constellations are Orion (the hunter), Canis Major (the big dog), Canis Minor (the small dog), Gemini (the twins), and Taurus (the bull). A number of interesting celestial objects that can be observed. This includes Sirius, apparently the brightest star in the sky next to our Sun, located in Canis Major, some deep-sky objects such as the Great Nebula in Orion, Pleaides (“the seven sisters”), and the Beehive Cluster in Cancer. Another is what is the well-known “Big Dipper” in Ursa Major (the big bear).
Figure 4. From top: Sirius, the Great Nebula in Orion; Bottom: Pleaides, and Beehive Cluster (Image Credit: Stellarium)
There are two asterisms being used by astronomers serving as indication of the astronomical winter. These are the Winter Triangle and the Winter Hexagon. The first one consists of the stars Betelgeuse (in Orion), Sirius, and Procyon (in Canis Minor). The other one composes of six stars, Rigel (in Orion), Aldebaran (in Taurus), Capella (in Auriga), Pollux (in Gemini), Procyon, and Sirius.
Figure 5. The Winter Triangle and The Winter Hexagon (Image Credit: Stellarium)
II. The Summer Sky
Conversely, distinct constellations and asterisms will be seen in the summer season. The main ones include the zodiac constellations Scorpio and Sagittarius. When you see these two, don’t hesitate to take great landscape photos of the Milky Way Galaxy, where its galactic core is located in between those constellations.
Figure 6. The Summer Sky. Encircled is the portion of the sky where the galactic core of the Milky Way Galaxy is apparently positioned (Image Credit: Stellarium).
Other fascinating deep-sky objects to be seen are the Trifid Nebula (in Sagittarius) and star clusters like Omega Centauri (in Centaurus) and the Butterfly Cluster (in Scorpio). If there is the Winter Triangle, there is also the Summer Triangle. This asterism creates an imaginary isosceles triangle encompasses of three vivid stars Vega (in Lyra), Altair (in Aquila) and Deneb (in Cygnus).
Figure 7. From top: Butterfly Cluster, Omega Centauri; bottom: Trifid Nebula, the Summer Triangle (Image Credit: Stellarium)
III. The Reason for the Seasons
You may be wondering, why do we see different set of stars in specific periods? Simple. The Earth is both rotating and revolving around the sun. Think of the Earth is spinning on its axis like a ballerina/ice skater, having a graceful dance around its massive partner, the Sun. Since it’s orbiting around the Sun, the Earth faces different portions of the celestial sphere in a particular time of the year.
Our general understanding of the seasons has significance to many aspects in our everyday lives. In spite of the modern time-keeping equipment, it had been used by farmers in determining when they will plant and harvest and also knowing when certain crops flourish. Some plants being planted during the summer are tomatoes, pumpkins, lantanas and periwinkles while cabbages, carrots, geraniums, and petunias grow during the winter .
Figure 8. Summer/Warm-Weather Growing Plants (Image Credit: static2.stuff.co.nz, commons.wikimedia.org, gardeningknowhow.com)
Figure 9. Winter/Cool-Weather Growing Plants (Image Credit: redwoodbarn.com, Flower Gardening Made Easy, Gardening Know How)
It has been a huge part of our daily lives in terms of conceptualizing goods, fashion, and events suitable for the particular season. For example, in the summer season, consumers tend to purchase more cold delicacies like ice cream and shakes while hot drinks and soups all through winter.
More comfortable clothes such as shorts, thin shirts, and swimwear are being worn by people during summer while thick-layered clothes like jackets and bonnets throughout winter.
Figure 10. Summer and Winter Attire (Image Credit: Egner Photography, Fashion Gum)
Some seasonal, traditional events that attract tourists or consumers are being held in some countries like the Dubai Winter Festival in the UAE  and the annual Fuyuzakura (winter cherry blossom) viewing in Japan  during winter. On the other hand, in summer, there is the Songkran Water Festival being held in Thailand  and several sales exist in malls due to the occasion when many people are travelling at this point in time.
In addition, it general helps us in preparing for its possible extreme effects or imminent natural disasters. It also gives a precise prognosis of weather patterns in different areas of the world. Multiple drought episodes and cases of extreme heat-related illnesses (e.g. heat exhaustion, sun burn) are occurring during summer while blizzards and hypothermia are some main concerns during the winter. More tropical cyclones tend to form when oceans became warmer (because of further solar heating) and affect such areas in summer than in winter .
Figure 11. Drought and Blizzard (Image Credit: agrihunt.com, Weather Underground)
Figure 12. Tropical Cyclone Climatology. Notice that tropical cyclones form in the summer until autumn months; June – December in the Northern Hemisphere and January – March in the Southern Hemisphere (Image Credit: aerospaceweb.org
The stars are not just beautiful entities that shine like diamonds in the sky. They are guides in time-keeping and organizing our respective life activities. There is a season, a time for everything under the heavens for every purpose.
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