It doesn't matter what time of day or what time of year. The animals are out on the safari everyday. Those that are penned at the end of the day are released from the night areas prior to the first safari of the day and are conditioned on feeding and auditory cues to move into their areas. Many carnivores sleep 18 or more hours a day regardless, so it you see the lions or cheetahs moving, it is just luck. The grazers are typically moving around because they eat all day. There is no truth to more activity in the early morning or evening, or not so much during the midday of the summer. They are African animals - it is hot in sub-saharan Africa.