Have you ever wondered what the weather in Midgard slum is like?
Ideally speaking, the plate will block the sun in summer and snow in winter, so it'd be cool in summer and warm in winter, right? Right?
WRONG.
Remember, the plate itself is a giant machine, and machine radiates heat. Also, I bet the plate disturbs the wind flow, too. So in summer, the slum would be like a basement on a hot day without a fan. The heat has nowhere to escape, and people get steamed alive in the slum.
In winter tho, that's where it gets tricky. Cos cold air tends to go down and stay in the lower ground, aka the slum. But the majority of snow will stay on the high ground, and I assume the plate will heat up to melt the snow to keep the upper ppl warm. The melted snow will probably go to the sewer and get dumped on the lower ground. Even if they don't have ice in the slums, they'd have dripping cold water or a lot of steam. So the winter in the slum likely has low temperature, high humidity, which is so much worse. If you live in tropical area, you'll know what I mean. The cold in humid weather is another kind of torture.
In conclusion, the humidity makes the slum even more extreme, hot gets hotter and cold gets colder. The plate is evil and capitalism is hell.