The Washington region is having its driest spring on record, stunting farm crops, turning many suburban lawns a shabby brown and creating conditions for dozens of forest fires.

Even the cooler weather that swept into the area this week will offer little or no relief from the dry spell. Forecasters predict a chance of rain tonight or tomorrow, but "we're not looking at any drought-breaking amount," said National Weather Service meteorologist David Caldwell.

"Trees are dying, vegetables are not doing very well, lawns are terrible," said Terry Bonfils, a horticultural expert for the Fairfax County Extension Service.

Only 3.47 inches of rain fell at National Airport from March 1 through the end of May -- about 35 percent of the 9.87 inches considered normal for the three-month span, said Weather Service forecaster Scott Prosise. It is the driest spring since the agency began keeping records in 1871. This year's spring showers amounted to less than half of last year's 7.7 inches of rain for the same period.

"It looks like July or August out there," said Bob Butterworth, Northern Virginia manager for Hydro Lawn, a lawn care firm.

Agricultural officials and farmers said the lack of rain could have a dramatic effect on the region's multimillion-dollar farm economy. The dry weather is scorching pastures and reducing hay yields. Some farmers were forced to sell cattle in April and May because of shortages of grass and hay to feed them, said Virginia agricultural officials. The water shortage prompted some farmers to plant corn, soybeans and tobacco ahead of schedule, but the crops' growth now is being slowed, according to agricultural agents. Many weedkillers are useless unless activated by rain. Some farmers say that the hot, dry weather is speeding insect maturity cycles, so they are now seeing tiny pests that usually do not appear until August.

"The weeds and the grass are growing, and nothing else is," said George Lechlider, the owner since 1946 of the 300-acre Leck's Farm near Laytonsville, Md. "You'll walk through fields where some of the corn is six, eight inches high, and some hasn't sprouted, and some sprouted and died."

Lechlider, president of the Montgomery County Farm Bureau, representing 870 local farmers, said that he had to stop planting soybeans because the ground was so hard and that he will have to spray expensive herbicide twice because the first application was not effective.

Lechlider's farm, like most others in the area, does not have an irrigation system, so he depends on rainfall to water his crops. Lechlider said his pasture grass is in such bad shape that it will not last much longer as cattle feed.

"If it stays this way for another 10 days, we'll have to start feeding them hay," said Lechlider.

He said his barley yield will be reduced because of the dry weather, and he expects to harvest only half of his usual crop of straw. Lechlider said his hogs do not like the dry weather any more than he does -- the dust congests their lungs.

Agricultural officials and farmers said the weather could lead to higher summer sweet corn prices, but they are uncertain how it might affect other produce and meat prices by summer's end.

The Fairfax County Water Authority is considering restrictions on weekend use of water because the system's pipes and treatment capacity cannot handle soaring demand, said James Warfield, deputy director of administration. "Last weekend, it seemed that everyone wanted to water their lawn on Saturday, not Sunday," he said.

Officials in other jurisdictions say they are not yet planning to impose water restrictions.

Last month, Fairfax water system customers used an average of more than 100 million gallons of water a day, compared with 86 million in May 1985, Warfield said. Lawn watering accounted for most of the increase, he said, noting that many of the county's new houses have sod-covered yards that require more water than established lawns.

At the National Arboretum, "We have the waters going like crazy," said Erik Neuman, curator of education. "We started having problems with water pressure."

Forests throughout the area are tinder-dry, and the number of fires recorded so far is the same as for the comparable period last year, which was among the worst ever, according to state park officials.

In Virginia, 1,600 fires have scorched 11,200 acres of parkland since Jan. 1, "considerably more than in a normal year," said Michael Griffin, forester for the Charlottesville region of the Virginia Division of Forestry. The most damaging burned 4,370 acres in the heart of Shenandoah National Park in early May.

In Maryland, 656 fires have burned 2,617 acres of forest this year, said Patrick Meckley, chief of resource protection for the state's Forest, Park and Wildlife Service.

The dry weather has not been all bad: "From the strawberry standpoint, it's been very good," said David Conrad, Prince George's County Extension Service agent. He said the dry conditions have protected the fruit from many of the diseases that flourish when the berries become wet.