Washington was graced Wednesday with another winter storm that looked grand through a picture window but was less pleasant under foot.

A glaze of ice made magnificent, shimmering art of the trees it encased but wreaked havoc with the commute in some places.

With most of it washed away by rain by midday, the question “How bad was it?” got an early ventilation. And once again, the answer depended on where you woke up. The weather fault line that bedevils the Washington region, and makes forecasters gray before their time, was at play.

Defining it, even in retrospect, invites condemnation because it squiggles more than any respectable line should. But the ice storm seemed more dramatic to the west of Interstate 95 than to the east.

There were cars spinning out all over, and people were bouncing on their buttocks everywhere, but the ice was most intense in the quadrant north and west of the District.

“And that’s been the case in all but one storm this winter,” said Jason Samenow, chief meteorologist for The Washington Post’s Capital Weather Gang. “This isn’t anything unusual. These areas average more snow and ice historically.”

Decades of weather data prove that point. Reagan National Airport records an annual snowfall average of 15 inches; more than 25 miles west of the District, Dulles International averages 22.

“The reason has to do with increasing elevation and distance away from the urban heat island, as well as influence from oceans,” Samenow said, speaking in general about the weather fault line. “I’m not aware of it in other cities, but I’m sure it exists.”

The average annual snowfall is 16 inches in Prince George’s County, 21 inches in Fairfax County and 22 inches in Loudoun County. The parts of Montgomery County closer to the District average 17 inches, while its northern reaches average 26.

“The roads were very icy, especially in the northern part of the county,” said Montgomery schools spokesman Dana Tofig, explaining the decision to close schools Wednesday.

The ice thickness varied, from roughly a 10th of an inch in the District to about twice that in portions of Northern Virginia and Montgomery, according to the National Weather Service. In Germantown, Sterling and Rockville, there was a quarter-inch of ice. Herndon had 0.13 inch of ice.

In Logan Circle, Ronald Byrd found little to slip on as he waited for a bus at 14th Street and Rhode Island Avenue in the middle of what Samenow called “the urban heat island.”

“It’s a typical rainy morning,” Byrd, 52, of Columbia Heights said, motioning to the uneventful street in front of him. “I kind of expected it to be actually worse than it is today.”

With relatively few accidents or downed power lines, it could have been worse. In 1994, the region was hit by a succession of ice storms. In 2002 and 2007, tens of thousands of people were left without power after ice storms.

Perhaps it is the dogged insistence that Washington is a region that causes such perplexity over the local weather. Kansas has its weather. Maine and Florida have their weather. The metroplex of Washington sprawls over a diameter of 75 miles and has all sorts of weather on any given day.

A region it may claim to be, but it is no more a weather region than it is a political one.

In large part, that may be a product of the fall line, a squiggly demarkation between the soft sediments of the coastal plain and the hard bedrock of the Piedmont.

The line it draws between Richmond and the Maryland-
Delaware border looks surprisingly like the route of I-95.

“It basically separates the coastal plain from the Piedmont and hills,” said Ian Livingston of the Capital Weather Gang. “So, much is elevation-dependent there. In cold-air damming situations like [Tuesday] night, the air mass banked up right against the Appalachians is always the slowest to dislodge as well.”

Livingston said the areas north and west of the District have felt more of winter’s bite this year that the rest of the region.

“More than normal, at least,” he said.

Donna St. George, Martin Weil, Patrick Svitek, Zach Cohen and Mark Berman contributed to this report.