How dry has it been? So dry, says Larry Coburn, he saw two trees chasing a dog down the street last week. A sustained, drenching rain would be welcome but there are benefits to the drought, too. Water levels are so low on the Potomac and Shenandoah rivers you can walk across in most places, the very thing for those who like to fish but don't have a boat.

"You can wet-wade just about anywhere on the river this summer," said Jim Gilford, who runs a tackle shop called the Rod Rack in Frederick, Md.

I called Gilford to see if he had any information on the upper Potomac's famous hatch of white miller flies, which come off by the millions at dusk some days during the last part of July and first half of August.

He said last week he witnessed the biggest hatch he has ever seen at the mouth of the Monocacy River. The little white insects swirled along the surface in thick clouds but the water was so low there was no sign of bass rampaging underneath to eat them, he said.

Usually a white miller hatch is underscored by a profusion of smallmouth bass dimpling the surface below, gorging on an easy meal. But the Monocacy was only ankle deep, too shallow and warm for bass, which must have moved downstream to deeper holes in the Potomac, said Gilford.

The following afternoon Coburn and I headed west up I-270 toward Antietam, where we hoped to intercept white millers hatching on the main river. He has seen the phenomenon several times but hasn't tired of it. I've seen it just once, near Point of Rocks years ago, when the flies came off in such abundance you had to cover your mouth to avoid inhaling them.

It's a mixed blessing from a flyfishing standpoint. In the midst of a white miller hatch bass are feeding everywhere but they've got so much to eat it's hard to elicit a strike. I remember pitching a white miller imitation into the maelstrom, aiming at rings in the water where bass were rising, but eventually giving up without a strike and settling back to watch the amazing summer snowstorm.

John Mullican, who works for the Maryland Department of Natural Resources in Western Maryland, said he's seen a couple of evenings like that already this year near Packhorse Ford, just above Antietam, which is where Coburn and I were bound. We followed State Route 34 from Sharpsburg down to the river, then took Canal Road along the old C&O Canal bed, winding along scenic two-lane blacktop under a canopy of shady green.

We got to Packhorse about 4 p.m. but Coburn, an expert flyrodder, judged it too shallow for good fishing. "Let's look at the mouth of Antietam Creek," he said.

The creek came in another mile or so downriver, with a handy riverside parking area and easy access via the towpath. We strolled across the old stone viaduct that once carried cargo barges over Antietam Creek on the trade route between Cumberland and Washington.

Coburn liked the look of the river there. Antietam Creek flowed in cool and fresh, mixing with the warmer water of the Potomac, and there looked to be deep holes aplenty. We assembled rods, tied on white miller flies and set out wading.

The river was 300 yards wide and refreshing on a hot day. Antietam Creek was downright bracing with a distinct chill as we waded hip-deep wearing shorts and Aqua-Sox. The bottom was rocky with patches of sand and stands of submerged grass; occasionally you'd spook a smallmouth from its hiding place but they mostly looked small.

Halfway out the temperature rose where the Antietam Creek flow gave way to the main river flow, and the irregular bottom grew even more so. Ooops! There was a nice hole, right up to my armpits.

I found a flat boulder and climbed up to respectable casting height. It was beautiful here, mountains looming to the west and the river gently flowing blood-warm 'round my legs. A few damsel flies buzzed by but I saw no sign of white millers. It was early yet.

Coburn waded 100 yards farther downstream and as usual started catching fish before I did. Seeing no white millers hatching, he switched to a white deer hair wounded-minnow pattern and twitched it across the surface. Small bass came up and smashed it.

I put on a small, chartreuse cork popper with rubber legs and twitched it and soon enough was sharing the fun. The fish were mostly eight to 10 inches with an occasional 12-incher thrown in.

Once in a while a bass would launch into the air to intercept a damselfly but the leapers were far apart. I found if you saw one, scurried into casting range, dropped a popper upstream and let it dead-drift into the bubbles where the bass had landed, it would often come back up and strike again. That led to a lot of fumbling around in unexpected deep holes but produced fish.

As dusk came on we waited for an explosion of white millers that never came. A few hatched and we saw some mayflies dancing around. Swallows zoomed along the surface scooping up bugs and a score of Canada geese swept in to a noisy landing. Flocks of wood ducks zoomed around in the sunset, as they do, and great blue herons croaked their prehistoric croaks from the banks.

Coburn caught a chunky, black 15-inch bass. Then it was dark. The moon came up to flood us in amber light and we lurched back to shore, holding hands to keep from falling in over our heads. Thank goodness no one was around to see that!

The white miller hatch is unpredictable but worth a try. Jim Gilford and his son Rob at the Rod Rack keep tabs on it and say it's been good around Brunswick and Shepherdstown the last few days, but comes and goes at various spots along the river from Hancock to Seneca Breaks in Montgomery County through mid-August. For updates, call the Rod Rack at 301-694-6143.

Whether you hit the hatch or not, wade-fishing is excellent on the river this time of year and the water is low enough to go almost anywhere. Some traditional hot spots: Pennyfield and Violette's Locks in Montgomery County; White's Ferry, Point of Rocks, Harper's Ferry and Antietam Creek.

Flyrodders should bring a six- or seven-weight rod, some white and chartreuse poppers and floating deer hair bugs, and some crystal buggers, woolly buggers and Clouser minnows for subsurface fishing. Spinfishermen should bring Tiny Torpedoes and small white and chartreuse buzzbaits for the surface, small white and chartreuse grubs and spinners, chrome crankbaits and small floating Rapalas for subsurface work.