Too hot to fish and too early to hunt, July snaps and sizzles its way into oppressive August. What's the outdoorsman to do?

Tradition has it that in weeks when the mercury tops 100 and the humidity hangs close to 100 per cent, Washingtonians desert the bubbling asphalt for two places - the seashore and the mountains.

In fact the exodus is almost all east, as motorist clog the Bay Bridge and the quiet blacktop two-lane roads that wind through the Eastern Shore's chicken farms and cornfields. For some perverse reason sunstruck people seem happiest when they are jammed together in the shocking glare of white sand, the surf pounding nearby.

The beach draws the crowds because it's easy - plenty of places to find. But for real escape from this endless summer, the painless two-hour drive to the mountains is as good an answer as any.

The hills are far from barren and empty. Plenty of city-dwellers find their way to the most popular trails and cool mountain streams. White Oak Canyon and Old Rag Mountain near Skyline Drive are as busy some weekends as the boardwalk at Ocean City.

But the mountains offer and quiet around each bend in the rail, and there each step up the hillside brings cooler air and crisper breezes.

Climbers know the scientific name for brisk conditions at the mountain-top - the adiabatic gradient. For every 1,000 feet up, the air cools off 3 degrees fahreheit, according to the equation. Tabulated that means the top of Old Rag at 3,291 feet should be about 10 degrees cooler than the nation's muggy, sea-level capital.

Add to that the 30-knot breezes that buffet the granite boulders at the peak and you have gratification, but it's far from instant.

A climbing friend and I did Old Rag last week, inspired by the description in the Potomac Appalachian Trail Club's priceless $1 booklet, "Circuit Hikes in the Shenandoah National Park.

Old Rag, said PATC, "is the most speetacular mountain in the Northern Virginia Blue Ridge. It is an outlying mountain, not part of the continuous chain.Views from the rocky ridge trail extend in all directions, including a noble panorama of the mountains in the central section of the Shenandoah National Park."

The panorama is indeed noble, but the effort required to get to where you can enjoy itis nobler still."This is really just a hike," said my partner, who has climbed real mountains. Nonetheless it was a weary, breathless hiker who brought up a distant rear by the halfway point up the ridge trail.

We were taking the roughest route up. The blue-blazed trail meanders up the most difficult sections in switch-backs, so that the grade never gets too steep. But vigorous climbers have bypassed the switchbacks with a direct route straight up, and we were picking our way along that.

The exertion was tempered by the shade of tall poplars and elms and occasional stops to munch on wild black raspberries or identify wildflowers from our field guide.

A third of the way up the growth changed from dense pine forest to tall hardwoods. Another third and we were dodging back and forth between broad outcroppings of boulders, from which the views were best, to paths through the forest.

At the halfway point was a spring and a note from an earlier climber: "Spring at top is dry: this is last water"

In all it was a tiring but uplifting day. Circuit hikes avoid the disadvantage duplication - our voyage out was as interesting as the one in. In six hours we were back at the car.

Many of the 22 hikes listed in the PATC booklet could be stretched easily into two or three day outings. The National Park Service permits primitive camping throughout the 200,000 acre Shenandoah Park, as long as tents are out of sight of trail and buildings. Georges are limited to 10, open fires are banned and any special regulations are posted.

The PATC booklet provides directions to all starting points, maps of the trails, estimates of distance and hours needed to complete each hike. It's available from the Potomac Appalachian Trail Club, 1718 N St. NW, or at most outdoor stores.

For those wedded to escape to the sea, the word from Ocean City is that the fishing is hot and getting hotter.

White marlin and tuna are being boated with regularity in the canyons way off shore. Eighty-two white marlin had been landed by last week, compared to only six in the same span last year.

Two big blue marlin were caught this month by Ocean City charter boats in the Baltimore Canyon. Robert E. Donovan of Rockville boated a 406-pounder on 50-pound test line.

A few broadbill swordfish reportedly are taking squid fished at night. The headboats are getting croaker, sea bass and a few tautog, and flounder fishing reportedly remains good.

And there's always the beach . . .