The question of when to go to Botswana is best answered by thinking about what you want to experience.
Game viewing is at its peak during the dry winter months of May to October when animals are concentrated in ever increasing numbers at water sources as the dry season wears on. Many experts regard the cooler months of June to August as the best time of year for a Botswana safari - the game viewing is consistently excellent, there's virtually no rain and the risk of malaria is at its lowest.
Reaching peak concentrations during the hot and dry September/October months, wildlife tends to disperse during the rainy January to April summer but several destinations such as Chobe's Savute region and the Kalahari offer excellent summer game viewing, not least because they lie on the path of migrating animals - particularly zebra. Indeed, Botswana's three Kalahari parks are arguably at their best in early summer - December is a particularly good month as many antelope give birth then which means more predators.
A year-round birding destination, bird watchers will nevertheless find the the migrant-filled summer months of the "Green Season" the best time to visit Botswana for both numbers and diversity of species.
WINTER OR DRY SEASON – April to September
Winter days in Botswana are extremely dry and sunny with temperatures reaching 25 °C during the day, and tend to fall to as low as 2 °C in the evenings and in certain areas hit below freezing at night. There is virtually no rainfall during this period.
SUMMER OR RAINY SEASON – October to March
During October temperatures can reach up to 40 °C or higher during the day and may drop to the mid 20 °C. Generally, the could cover and first rains arrive by the end of November into early December where things begin to cool down for a short time. The rainy season lasts until the end of February into the beginning of March and these days tend to be hot and sunny in the morning with late afternoon thunderstorms and odd downpours.