I'm in the middle of a rainforest and am soaking wet. Not from rain – I haven't seen a drop all week – but from jumping into the babbling Hoh river in Washington state during a rafting trip with Rainforest Paddlers. Bobbing in a life-jacket past stands of moss-shrouded evergreens is an easy way to cool down after paddling furiously through rapids and baking in blazing sunshine.
Like the spreading big-leaf maples and majestic Sitka spruces lining the river banks, the Hoh's deliciously cool waters owe their existence to the Olympic mountains behind me. Rising to 8,000ft, the peaks at the heart of the Olympic National Park trap moisture rolling in from the Pacific Ocean, making the lush foothills the wettest place in mainland North America.
Hardly the most attractive place for a week's outdoor holiday, you might think. But the Olympic peninsula receives most of its rainfall from September to May, leaving the summer largely hot and sunny.
To maximise the chance of dry weather, I started my Olympic odyssey on the east side of the park, in the rain shadow of Mount Olympus. At 5,400ft, Deer Park is the highest and driest campground in the Olympics: it gets only 10 per cent of the rainfall of the forest 30 miles away. Trails wind out from here through deep valleys and along dramatic ridges, criss-crossing 1,500 sq miles of virtually pristine wilderness – the same size as Essex, but more invigorating.
My first long hike, a 15-mile walk traversing Green Mountain, Maiden Peak and Elk Mountain, was a roller-coaster ride through silvery lodgepole pine forests, steep shale slopes and sub-Alpine meadows carpeted with wildflowers. In the distance, jagged snow-capped peaks sparkle, while the only sounds are the rush of mountain streams and the whistle of the shy Olympic marmot. Apart from a party of bumble bee scientists and a volunteer tracking those elusive marmots, I passed just one other pair of hikers.
Back at sea level the next day, I explored the peninsula's northern coast. Dungeness Spit, named after the beach in Kent, is America's longest spit, a five and a half-mile finger of sand pointing at the neighbouring Canadian island of Vancouver. I aim for the lighthouse at the tip, then walk for hours through giant driftwood trunks with water on either side.
My busiest day yet was a trip with AT Kayaking in Port Angeles. Bright and early, I climbed into a kayak and paddled out into the Strait of Juan de Fuca. Our eight-mile paddle took in numerous bays and coves along the craggy shoreline, hunting for starfish in rock pools, spotting racoon feasting on shellfish and disturbing a pod of sun-bathing seals.
In the afternoon, the company owner, Tammi Hinkle drove me into the foothills to tackle the Olympic Discovery bike trail. Over the past few years, this track has been carved through the forest by a chain gang from the local county jail. It offers a (mostly) downhill, high-speed slalom that's suitable for beginners but with enough switchbacks to give technical riders a thrill.
The park's hot springs sounded very attractive. A resort at Sol Duc has concrete pools, filtered water and massages, but I hiked a couple of miles to the old Olympic Hot Springs. Closed since the Seventies, this tiny resort has returned to nature, with a dozen secluded pools steaming gently amid ferns and swaying alders. Alternating soaks in the sulphurous spring waters with dips in the glacial meltwater of the Elwha River below proved more stimulating than any health spa therapy.
All week, I'd camped at National Park campgrounds. Some have running water, others just a vault toilet, but all are cheap and welcoming, with fire pits, picnic tables and often stunning views.
For my last night, I splashed out on a stay at Lake Crescent Lodge, a 1916 hunting lodge with elk heads on the walls, a panelled saloon and a lake where the sun sets behind tree-lined mountains. More important, it has hot showers and ice-cold beers. For those factors alone, I awarded it my own personal Olympic gold medal.
BA (0844 493 0787; ba.com) offers the only non-stop flights from the UK to Washington State, flying from Heathrow to Seattle. The Olympic National Park begins 80 miles from the airport. Campgrounds in the national park (001 360 565 3130; nps.gov/olym) cost $10-12 (£6.60-£8) a night per site, for up to eight people. Lake Crescent Lodge (001 360 928 3211; lakecrescentlodge.com) offers doubles from $118 (£79), excluding breakfast.