May - August : winter
September - November : summer
November - March : spring
April - May : fall
Right now, October, is the peak of hot season. It's when temperatures are highest throughout the country. It's also dry season which us typically from April/May to November. This means that it won't rain during this period. Most of the vegetation during dry season turns brown and dies. There are some trees though that actually sprout leaves and produce fruit.
The rainy season usually begins in November. When the rains finally arrive I consider this spring because everything starts to turn green and it rains a lot, similar to spring in the states. Rainy season is when planting occurs. The livestock are particularly happy and fat at this time, too because of all of the fresh grass. During dry season they grow thin due to a lack of food from burning, etc. Temperatures are still hot during midday but they're tolerable, unlike now when there are days when all you can do is lie on the floor and sweat while hoping for the temperature to drop (hint: it usually doesn't and you end up tossing and turning in a pool of your own sweat).
During April or May the rains finish and temperatures drop. July is the coldest month. There are mornings when I can see my breath and wear multiple layers and slippers. Many days are overcast and windy. Zambians don't like cold season and to be fair, there are a lot more funerals during this time of year. Whether or not they're weather related I'm not sure.
So, that's a brief rundown of my experience with Zambia's seasons. I'm not a fan of hot season and tend to become grumpy and unpleasant because of the heat but cold season is nice. Too bad it's so short. It'd be fine with me if cold season lasted right up until rainy season began!
