You will spend all of your time in the Northern Serengeti where the winter (June/July/August) mornings can be very cold however they warm up to nice sunny winter mornings from mid morning onwards.
In spring (Sep/Oct), it’s very dry therefore the day temperature can rise rapidly and it can be very hot around midday. The temperatures are mostly pleasant, with nighttime temperatures dropping down to 4-9°C (40-50°F) and daytime temperatures occasionally reaching up to 24- 27°C (75-80°F)