Undecided for me. I'm flirting with the idea of making my small little corner of the world into a very dense & dirty urban setting. By packing as much structure into it as possible, with tightly clustered buildings, and street overpasses. I don't see much room for much natural growth except maybe some weeds and small bushes or saplings. So if I ultimately decide to go that route. I could say that it is pretty much anytime of the year. It could be -10 it could be 40 degrees Celcius. Take your pick its still very dense and dirty day in the city.