Imagine going on an expensive safari only to find you've landed in the rainy season. Not a good result, you might think. But in southern Africa it could be a smart idea. All the guide books will tell you why the dry season is best: a lack of rain means that wild animals are forced to gather around watering holes, making sightings easy and predictable. With vegetation parched, it's easier to see big cats slinking through the grass.
So why are some experts suggesting that we visit during the rains? It's not just because the game parks are uncrowded and the prices lower. "The rains bring an incredible sense of replenishment to the region, with an explosion of vibrant colour, thriving vegetation and swollen rivers," says Will Bolsover, a former guide who now runs his own safari company. "In countries like Zambia there is still plenty of game to see, plus you have the added excitement of electric storms, colourful birdlife and more of a sense of adventure."
In Zambia's South Luangwa Valley some operators close their camps between January and Easter, but a few are now keeping them open throughout the wet season, which they have cunningly rebranded as the "emerald season". In the first week of April towards the end of the rains, I arrived at Nkwali, a luxury camp on the banks of the Luangwa. It was full, mainly of khaki-clad Brits swapping stories of the big game they'd encountered that morning.
Although it was the wildlife we had all come to see, it was the river itself that became a constant source of fascination. During the dry season between May and November the Luangwa is little more than a trickle, much to the distress of the thousands of hippos that live in it. All night you can hear them grunting and squealing as they squabble over wallowing rights.
By April the river is close to bursting its banks. Dead trees are swept along in its slick currents and, beneath the surface, herds of hippo harrumph contentedly, only their snouts and small round ears visible.
At Nkwali, where the Luangwa is as wide as four football pitches, our morning and evening game drives began with a boat ride to the opposite bank, the entry point to the South Luangwa National Park. There, we would climb into open-topped, open-sided Land Cruisers, hoping the rain would hold off.
We were lucky. Not only did we dodge the showers but we were treated to the most startlingly beautiful African skies: fiery orange sunsets, cloudscapes that could have been painted by Magritte and, after dark, lengthy electrical storms that strobed the skies with sheet and fork lightning.
With the vegetation running riot, I had been cautioned not to expect to see many animals. But again we lucked out. Just five minutes into our first drive we turned a corner to find a pride of lions stretched out on the road in post-prandial bliss, rolling on their backs and licking their paws. Our driver killed the engine, and humans and cats all eyeballed each other silently for several minutes before the lions sauntered off.
Close encounters with elephant, giraffe, puku and zebra all followed. Then, as darkness unfolded and a dazzling view of the Milky Way appeared above, our guide switched on a powerful arc light that revealed owls and genets, hyenas and hares. We didn't spot any leopard, nor the wild dogs, but there were no complaints.
If the animal count was down a tad, the bird count was soaring. I've never quite understood the appeal of birdwatching but even I was struggling to remain blasé in the face of such ornithological extravagance. The colourful local population - many of them strutting about in their full breeding plumage - were joined by dozens of species of migrating birds. One birder in our group was almost hyperventilating with excitement, ticking off lilac-breasted rollers, paradise whydahs and southern crowned cranes. "Incredible," he panted, "whole breeding colonies... thousands of them."
Further up the valley is another camp that stays open throughout the wet season. Tafika has just six rustic cottages in a remote riverside clearing three miles from the nearest village. With the surrounding roads impassable, the only way to reach the camp is by motor boat.
The two-hour journey upstream from Nkwali had a Conradesque quality to it. Each bend in the river took us deeper into the wilderness, the only signs of human life a couple of fishermen paddling dugout canoes. Every now and then the boatman would cut the motor to point out crocodiles lurking in the shallows or African skimmers darting across the surface of the water, their beaks wide open to catch small fish.
John Coppinger, who owns and runs Tafika with his wife Carol, met me at the jetty with a muscular handshake and a warm smile. He showed me to my cottage - hand built using thatch and bamboo - and we lunched on chicken and mango salad, spinach tart and home-baked bread.
Coppinger is a pioneer of rainy-season safaris. Between February and April, when the river is at its most swollen, he cancels his usual programme of game drives and instead runs river safaris. Guests travel by canoe or dinghy across floodplains and seasonal lakes to remote spots where, with a guide and armed scout, they head off walking deep into the bush.
Later that day I joined the only other guests - two middle-aged sisters - on canoes and we paddled gently downstream, slowing to watch fish eagles, malachite kingfishers and a pair of watchful buffalo. A newborn hippo trotted along the bank behind its mother - evidence that even the least attractive creatures can have cute kids.
Stephen, our guide, showed us how to tap the bottoms of the canoes with the paddles. "It's to warn the hippos," he explained. "When they come to the surface they can't see what's above them. If they tip your canoe over and you fall in, the crocodiles will get you." This is not a happy thought, so we did as we were told and tapped.
Soon after dawn next morning we moored the dinghy downstream and hiked through the chest-high grass along what, at first glance, looked like well-used footpaths. In fact, they were trails cleared by hippos on nocturnal food hunts. Stephen pointed out lion droppings and the velvety-soft elephant ear that local villagers use as toilet paper for babies.
After an hour and a half we reached a colony of yellow-billed storks that return each year to hatch their chicks in the same half dozen ebony trees. We sat nearby under a winter thorn, drinking tea and eating ginger cake, as hundreds of the huge birds flapped, squawked, squeaked and scrapped. They made such a din we could barely hear each other speak.
Back at base camp a treat lay in store. Coppinger, a former commercial pilot, is the proud owner of a two-man microlight and, providing conditions are good, he will take guests on spectacular low-level flights over the valley.
Strapped into the passenger seat, a huge involuntary grin broke across my face as we bounced off the grassy airstrip and soared skyward. It was an awesome sight, the whole valley laid out beneath us, the course of the Luangwa, its tributaries and oxbow lakes suddenly clearly visible. "Look at it," said Coppinger over the intercom, "the last great untamed river in Africa."
We flew to a height of several hundred feet where we could see a rainbow and distant storms, then dived down through the treetops to watch baby elephants bathing in a riverbed. We passed over the yellow-billed storks - taking care not to disturb them - and Coppinger pointed out giraffe, buffalo, waterbuck and eland. "Amazing, isn't it?" he sighed. No further commentary was required.
Mark Hodson is editor of 101 Holidays