Week 1 - 90 to 95
Week 2 - 85 to 90
Week 3 - 80 to 85
Week 4 - 75 to 80
Week 5 - 70 to 75
Week 6 - Fully feathered out - Good to go.
In spring and summer I usually turn the heat off after about 4 weeks. It does not usually get below the low 50's at night and I have enough that they can huddle to stay warm if the want to. They huddle even when it it ridiculously hot at night. They just like to sleep in a pile. My brooder is in my coop.
I also keep one small spot at these temperatures and let the rest of the brooder be cooler. For example, when I put them in the brooder straight from the incubator, the area under the heat lamp is in the low 90's but the far corner is about 70. The first couple of days they tend to stay mostly under the lamp, but by the third day they are playing in the cooler far corners, coming back to the lamp when they need to warm up.
I would not take any chicken straight from tropical temperatures straight to below freezing temperatures, but give them a time to adjust.