Human society has always been, by and large, determined by weather and climate. These factors decided where crops could grow and which places were most hospitable during the year. Throughout human history, this has been in the temperate or tropical bands near the equator as the poles denied all but the most extremophilic, or best equipped, portions of humanity.
The climate catastrophe forced humanity to abandon the cradles of its longest and oldest societies. The exodus to the far north, as the soil decarbonised and the deserts expanded, led to the development of an entirely new world. Previously humanity had been used to a cycle of day and night that, while not perfectly balanced, at least was close. Days might be longer in summer and shorter in winter, but the extremes were still manageable. In the north, the days and seasons are nearly synonymous. In all but the very edges of the New World, the summer might see an hour of the sunset while winter sees an hour of sunrise. Once you get into the arctic sea proper, in the northern edges of the Duty-Free Ports of House 'Bacco and Nazzdack, the sun only sets and rises once a year.
In this future north, the weather is always extreme. Massive storms and powerful hurricanes define autumn and spring as the depth of winter yields slushy and sudden frosts that can strike even in the warmest parts of the world. While the world, as a whole, is far hotter and the north is generally tropical, the weather is also far more extreme in its impact. A hurricane can give to a short, killing frost that melts before the following day has finished. Thus, attempts to predict the weather is foolish a prospect at best since, at most, one can get a few hours warning before a storm system spins into existence. The dark months, in particular, mean different things in different parts of the world. However, to everyone, it is defined by whether or not the day or night is bearing down on the Earth's axis. As the Earth orbits the sun, the sunlight's exposure on the north pole varies. This shifting exposure leads to an exchange of hours spent in the light or dark during a given season. Thus, when the Earth's orbit causes both day and night to be bright, it is summer. However, winter arrives when both day and night are dark.
When light shines upon it, parties are outdoors with people running around sunbathing and surfing, taking joy in outdoor activities while they still can. The summer is the heaviest growing season, with farms making a great effort to bring in the harvests as quickly as possible before the days begin to shorten again. The days are focused on hard work and hard partying, with people heading out of their homes, sluicing out of their sense tanks, and heading to the beaches and outdoor party scenes. Gobbo grifters, Corpo shop runners, and advertisement agencies get their best business done during this prosperous period of the year.
However, as the sun sets and autumn starts, the party gals and guys head indoors to shelter against the oncoming hurricanes. Indoors their fury is drip-fed by the remnants of the summer heat and energy bleeding off. When the worst of the storms have passed, it is well into autumn. The sun is steadily setting, the day and night cycle reaching equilibrium for most of the world as it prepares to switch places. The dark months have begun when the goths and spooks are out to play. With the torpor of autumn, the competitive season for sports teams comes to life for its now unoccupied audiences. Revellers find their last chance to party in contests and festivals unique to the traditions of each region. Winter begins when the sun's last light shines on the north pole. Here the longest nights have begun, causing the people to retreat indoors. No one can suspect if the outside will have a burning hot day, a chilly terror, or even a killing frost that will burn away as soon as the sun briefly rises for a few hours.
Winter is the season of raves and indoor assignations. In these months, the underground denizens begin to come out to play more often, seeking to trade or enact their strange and spooky ways on the ones above. In the winter, the absence of the sun's beating UV light leads to fresh waves of monstrosities emerging across the New World (including the infamous Spider Nikolas and his mutated candy-floss-web spinning flying reindeer). These creatures, wrought from automated biofactories, are safe from cellular degradation caused by the overbearing UV light of day.
Spring marks another wave of storms, less severe than those in autumn, and the planting season begins for many plantations. The gothy types retreat to their homes, and the people stuck with cabin fever from the long dark months head out. Storm surfers go out to try their luck, gobbos come out from hibernation away from their slow, lazy times under UV lamps to go out and get some proper sun. The party boys and girls move from the rave scene to the beach scene once again. Monster hunters finally get a break from the waves, born during the winter, of mutants and creatures prone to UV light. Exposure to the harsh sun causes bacterial infections within their leprous bodies to grow and fester, breaking down those who refuse to retreat.