The climate in Game of Thrones is incredibly weird, not least because of the strange timing of the oddly-long seasons. A group of climate scientists from the Universities of Bristol, Cardiff, and Southampton decided to figure out what's going on by making a climate model of the world -- based on the weather data they could scrounge from George R. R. Martin's novels. They wrote it up as a mock academic paper authored by the GoT character "Samwell Tarly".
Their/his key finding? The only way to create a model that behaves like the world described in the books is to assume the planet in Game of Thrones "tumbles" as it orbits its sun:
One way that seasons can be made to last longer is to allow this tilt of the spinning axis to change throughout the year, so that the Earth ‘tumbles’ on its spin axis, a bit like a spinning top. If the Earth ‘tumbles’ exactly once in a single year, then the spin axis always points towards (or away) from the Sun, and the winter (or summer) is then permanent (Figure 3(b)). This extended winter or summer would come to an end if the tilt flipped such that the opposite hemisphere pointed towards the sun. [snip]
In terms of the transition between the two seasons, my assumption is that the planet is fixed in a permanent season over several years due to the tumbling of the tilt 60 of its spinning axis, but that the tilt flips every few years to give the opposite season. The reason for this flip is unclear, but may be a passing comet, or just the magic of the Seven (or magic of the red Lord of Light if your name is Melisandre).
It tunrs out that various parts of Game of Thrones world bear similarities to the climate of our real-world earth (minus the magic and weirdly tilting planet, of course). In winter, The Wall resembles parts of Alaska, Canada, western Greenland, and Russia; meanwhile, Casterly Rock is kind of like eastern China and Houston, Texas.
The scientists also found that "the modelled climate can be used to explain the likely attack plans of invading dragon hordes from Essos, the dominance of the seas by the Iron Fleet, the hibernation zones of White Walkers in summer, and the trading routes between Westeros and the 30 Free cities across the Narrow Sea."
Given today's climate-change denialism, there's a sly political aspect to the work here, as the authors note: Their project shows the "flexibility of climate models, arising from their basis in fundamental science." (Emphasis all mine.)