Botswana's Dry Season = Safari "High Season"
Botswana's dry season generally falls between May through October. It's also "winter" which is relative in Botswana, as you can still expect day time temperatures to reach around 68 Fahrenheit (25 Celsius). It does get chilly at night, and your morning drives in July and August will call for layering. If you plan to visit the Kalahari, you can expect some really frosty mornings and chilly evenings during those months. By October however, the temperatures are on the rise and it can be very hot, around 104 Fahrenheit (40 Celsius) during the day. It's generally still a dry heat, so bearable, but be prepared for some strong sun and book a camp/lodge with a pool.
The dry season is the best time to view wildlife. The animals are easy to spot over longer distances because the grass is short, and the bushes aren't bushy. They also gather in larger herds to drink from the few remaining water sources. But the dry season is busy as it also coincides with the summer holidays for the northern hemisphere. Expect prices to be higher and plan to book your safari at least six months (if not a year) in advance. Botswana is an amazing safari destination because many of the camps are small and you have to charter a plane to get to them. This puts a premium on space since there's no such thing as mass tourism in Botswana.
The Okavango Delta is at its ultimate best during July and August. The flood waters have made it down into the delta, attracting huge numbers of wildlife from the dry interior. You'll see huge herds of elephant, buffalo and all manner of ungulates, followed by the predators who love them so.
The dry season also means it's less humid and therefore buggy. If you are concerned about catching malaria, then visiting Botswana in the dry season is a good option.
Botswana's Green Season = Safari Shoulder/Low Season
Most of Botswana's rainfall occurs from December to March. Some years it can come early, sometimes it doesn't come at all. But when it does, the landscape completely transforms and it's a beautiful sight. Keen birders wouldn't consider coming to Botswana at any other time of year. The rainy season also spawns a baby boom. If you love seeing tiny warthogs, infant zebra and baby impala, this is the time of year to go. The disadvantage is that the wildlife becomes a little harder to spot behind dense bushes and taller grass. This can actually make a safari less predictable and more exciting in my opinion. And there's always something to see of interest in the bush. But you can't expect to see large herds during this time of year as the animals disperse to forage and move to the greener interior area.
Botswana goes on sale during the green season and this may be the best reason to go during this time. Many of the camps stay open, because you fly in anyway, so road conditions don't matter as much as say in Zambia or Tanzania during the wet season. The odd thing about the rainy season, particularly in the Okavango Delta, is that it dries up from the annual flooding. So some camps are unable to offer a water-based safari experience.
Botswana is 80% desert, so don't expect monsoon conditions during the rainy season. You'll likely have a downpour or two during the day (usually in the late afternoon) and then it will be sunny again. Be prepared for a little more humidity in the air and more bugs, including mosquitoes.
The In Between Months - November and April
I was in Botswana recently in November just around the time of the first rains. November is an unpredictable month to say the least. It was very hot, around 38 Celsius during the day. I saw a huge amount of wildlife (some very skinny), but the earth was parched. The very dry conditions meant that there was a lot of dust in the air, so taking good photos proved a little more tricky. It was easy on my budget so I got to stay longer, but some of the camps were almost too empty. When the first rains came on my last day, it smelled wonderful, baby warthogs appeared out of seemingly nowhere, and temperatures cooled to perfect.
April is a wonderful time to visit, you get the benefit of lower prices, but the air is nice and clear, and the bush is still lush. It's the best time to go if you're a keen wildlife photographer.
Best Time to Visit the Kalahari Desert
If you wish to spend some quality time with the San bushmen, the Kalahari desert is best to visit during the cooler, dry months between May and September. October can get too hot. However if you're looking to do some wildlife viewing or birding, the rainy season is best. It's difficult to get around though and some camps even close from January to April, especially those around the Makgadikgadi Pans.