“A wizard did it.”
What might that fantasy explanation be? Here’s where we affix our tinfoil hats firmly to our heads.
The best place to start is by recognizing that the duality of the seasons—long summers vs long winters—is reflected all over the story. Most obviously, it’s reflected in the title of the saga itself: A Song of Ice and Fire, ice being winter and fire being summer. We also see it in the religion of R’hllor. Adherents like Melisandre believe that there are two gods: R’hllor is the god of light, heat, and life, and the Great Other is the god of cold, ice, and death. Melisandre brings up duality constantly, whether she’s educating Davos on her view of morality (“If half an onion is black with rot, it is a rotten onion. A man is good or he is evil.”) or beseeching her god for favor (“The night is dark and full of terrors…but the fire burns them all away.”)
According to Melisandre, the two gods of her religion are locked in constant conflict, and their war will effect the lives of everyone on the planet before it is done.
"“The truth is all around you, plain to behold. The night is dark and full of terrors, the day bright and beautiful and full of hope. One is black, the other white. There is ice and there is fire. Hate and love. Bitter and sweet. Male and female. Pain and pleasure. Winter and summer. Evil and good. Death and life. Everywhere, opposites. Everywhere, the war. There are two, Onion Knight. Not seven, not one, not a hundred or a thousand. Two! Do you think I crossed half the world to put yet another vain king on yet another empty throne? The war has been waged since time began, and before it is done, all men must choose where they will stand. On one side is R’hllor, the Lord of Light, the Heart of Fire, the God of Flame and Shadow. Against him stands the Great Other whose name may not be spoken, the Lord of Darkness, the Soul of Ice, the God of Night and Terror. Ours is not a choice between Baratheon and Lannister, between Greyjoy and Stark. It is death we choose, or life. Darkness, or light.” —Melisandre, A Storm of Swords"
So Martin makes duality a central theme of the series. He puts it in the title. He makes it a fact of life for many characters by forcing them to suffer through punishingly long seasons, and he gives lengthy speeches about it to one of the only characters who can claim to have genuine magical powers. I think he’s signaling that it’s all connected, that the tension between R’hllor and the Great Other, between winter and summer, between ice and fire, is all part of the same war. And if all of these conflicts are really one conflict, solving one will solve the others. In other words, the resolution of the war between R’hllor and the Great Other may normalize the seasons.
Mind you, I don’t expect we’ll see R’hllor take on the Great Other in any sort of literal fashion. We already have our players in place. Instead, the war will be fought through their proxies, and it’s not hard to guess who they are. The White Walkers represent the Great Other—they are ice, they are winter, and they are coming. The dragons are fighting for R’hllor—they are light, they are summer, they are “fire made flesh.”
Literally, this means that we’ll likely see a battle between the White Walkers and the dragons before the story is over, but you didn’t need to analyze Martin’s use of metaphors to guess that. We can also work backwards and make some guesses as to how these being affect the seasons on planet Westeros.
Theory: Westeros has erratic seasons because whatever dueling magical forces that animate White Walkers and dragons have been thrown out of balance
As the embodiment of winter, the White Walkers bring the cold with them wherever they go (some characters theorize that it’s the other way around, but either way, White Walkers = winter). The first time the people of Westeros got a taste of this was during the Long Night, a period in which there was a winter “that lasted a generation,” according to Old Nan. During this time, the White Walkers ravaged Westeros, but were beaten back by a legendary hero under nebulous circumstances, likely with an assist from the Children of the Forest.
The takeaway from the Long Night seems to be that winter goes where the White Walkers want it to go. We don’t know much about what went on between the White Walkers in the 8,000 years since the Wall was built, but it’s possible that winter befalls Westeros whenever they start getting antsy and begin making moves toward the Wall.
Recently, they’ve upped their game, as evidenced by the wildlings fleeing south and the Night’s King assembling a new army of the dead at Hardhome. Game of Thrones begins toward the end of the longest summer many of the characters can remember, and some think that foretells a long winter. Under this theory, the long summer was the result of the White Walkers biding their time while they gathered their strength, and the long winter, if it comes, could be the result of them making a big push to get over, around, or through that damn wall. There’s something different about their efforts this time—they mean business. If they made swipes toward the Wall before, they were weak.
So what kept the White Walkers, and by extension winter, in check for the last 8,000 years? Their opposite: the dragons, the agents of summer. If the White Walkers, or whatever power if tied to them, can extend the winters in Westeros, then perhaps whatever power is associated with the dragons can extend the summers.
Humans first encountered dragons on the Valyrian peninsula some 3,000 years after the Long Night, in a network of volcanoes called the Fourteen Flames. However, the dragons were likely thriving for many thousands of years before that. Dragons and White Walkers are metaphorical mirror images of each other; they’re both magical creatures, but they embody opposite values: light and dark, life and death, etc. I’m willing to bet that dragons and White Walkers have been denizens of planet Westeros for around the same amount of time. Even though they’ve never come into direct contact, they’ve been waging the battle on behalf of R’hllor and the Great Other for many millennia.
Okay, but what does that have to do with the seasons? I think that, at one point, the seasons in Westeros repeated at regular intervals, as they do on Earth, but that something disrupted the balance. I think this something was the Long Night, when the the White Walkers—the embodiment of winter—decided to shake things up and head south.
Since the First Men didn’t keep detailed records, there are no accounts of what the seasons were like before the Long Night, but there is some (very) circumstantial evidence that they operated differently. For example, before the White Walkers first made themselves known, the people of Westeros built a series of architectural marvels, including Winterfell, Storm’s End, the Hightower, and Casterly Rock. Remembering our note from earlier about the difficulties of industrialization in Westeros, I find it hard to believe that they could have built these structures if they were preoccupied with preparing for the next unpredictably long winter.*
Then came the Long Night, when the White Walkers left the sphere set aside for them and unleashed their power on the wider world. They brought with them a winter that lasted a generation, and forever threw the the balance of the seasons out of whack. Rather than sticking to the ordinary schedule, R’hllor and the Great Other now had to fight for control of the climate. One of them would be on top for a while, and then the other one would knock him down—there was no predictability anymore, and the seasons responded accordingly.
And yes, this theory basically suggests that the epic battle for the fate of the world a large-scale version of the political rivalries that dominate court life in King’s Landing. Gods—they’re just like people, only bigger.
Explaining Westeros’ weird weather patterns in terms of the ongoing battle between R’hllor and the Great Other could also explain why the White Walkers are only now making a concerted effort to invade the lands beyond the Wall. As we know, dragons had been dead for over a hundred years before Daenerys hatched her three eggs. With his representatives in the world gone, the power of R’hllor weakened during this time. As representatives of the Great Other, the White Walkers knew it, and chose to strike.
As mentioned above, I say all this with a tinfoil hat firmly affixed to my head. The truth is that we won’t know exactly what’s behind the erratic seasons until George R.R. Martin reveals it, probably in A Dream of Spring. Until then, enjoy the winter.
*The hole in this argument is the Red Keep, a fantastic structure that dominates King’s Landing. Construction on the Red Keep was begun by Aegon the Conqueror long after the erratic seasons had been established. Still, Aegon didn’t survive to see it completed, so maybe he was content to build it very, very slowly. Also: his dragons may have kept winter at bay for a while, and King’s Landing is far enough south that the winters may not have been brutal on the construction process.