Hello,
As far as I know, many construction companies are only just starting to build now - so it is theoretically possible.
I would not do it for the following reasons:
1. According to the weather forecast, we should already have below freezing temperatures here in Berlin/Brandenburg in 2 weeks
- I would be afraid of casting the foundation slab during frost. I cannot imagine that it would not involve any risk. And the foundation slab is very, very important for the house. If something goes wrong there, then good luck...
2. It is also not great if all the moisture gets into the house. If you start building now, you can be glad if you have a roof by December. The windows are probably no longer feasible. But if that doesn't work out, then your building structure will be exposed to the entire weather from December to February/March...
When would I still build now:
1. If you probably do not have below freezing temperatures during the curing of the foundation slab
2. If you get your house "weather-tight" (windows, roof) before the bad and cold weather sets in.
What would also be possible:
You do the foundation slab this year and the rest next year.
I am not a specialist in this field. But I would definitely recommend that you contact a Bausachverständigen and ask about this topic. Many will surely provide such information for free.