The dry season in Zimbabwe is from April to October, with the rains falling from November through to March.
In general however, game viewing in Zimbabwe is best between June and early November. In April/ May, the grasses are still long and the animals are more spread out, so game viewing can be more challenging. From June onwards, the game viewing can be considered as excellent, though it is absolutely best from August to the end of the dry season in October.
The landscape can look harsh and very dry during this time, but game viewing is easiest because grasses and foliage have withered or being eaten, and animals are reliant on more limited water sources. Migrant birds tend to start arriving in late September.
November usually brings the start of the rainy season, and whilst game viewing can still be excellent with great visibility, certain animals (particularly elephant and buffalo herds) will start to disperse as soon as enough rain has fallen for them to survive away from the permanent water sources.
The most challenging time of year to visit Zimbabwe is from December to March, unless you are mainly interested in birds and don’t mind some rain!
Temperature-wise, Zimbabwe is temperate (not too hot or cold) in April and late August/ September. May through to late August is lovely and fresh, with clear sunny days but very, very cold evenings and early mornings. From late September onwards it can get very hot with day temperatures often exceeding 35C and humidity increasing until the onset of the rains in November when temperatures drop off a little. December to March can be very hot and at times, humid.
The best time to view Victoria Falls is between March and June when the flow over the falls is at its highest.