The worst drought in 30 years is fueling dangerous brush fires across the Northeast. Although firefighters finally extinguished a roaring blaze near West Hampton on New York's Long Island, the fire danger throughout the region remains high because of a widespread lack of rain. From Quebec to Maryland, the flint-dry conditions are leaving homeowners with brown lawns, farmers with stunted crops, and some residents with the unpleasant taste of burning woodlands in their mouths. So far it is New York's driest August on record. It has not rained in the metropolitan region for 20 days.. The drought is considered ''extreme'' in Delaware, coastal New York and Connecticut, the Pocono Mountains in eastern Pennsylvania, and the southeast shore of Maryland. the situation is exacerbated by low snowfall this past winter, says Kathryn Vreeland, assistant climatologist at Cornell University's Northeast Regional Climate Center. Conditions are not likely to change anytime soon. ccording to the forecasts from the National Weather Service, most of the Northeast can expect clear skies through Labor Day. ''We are staying in a northwest flow that will keep the dry air heading across New England,'' says Russell Martin of the weather service in Camp Springs, Md. ''This will keep precipitation to a minimum.'' The weather is likely to be ideal for the long Labor Day weekend, but there are likely to be restrictions on barbecues and fires. The importance of the restrictions was underscored last week when brush fires roared across 6,000 acres on eastern Long Island. The wind-driven flames destroyed property until federal, state, and local efforts brought it under control on Saturday. Arson is suspected. Forest fires are a problem in other areas as well. In Quebec, the worst fires in 40 years have destroyed about 1 million acres of timberland. With the smoke drifting as far south as Portland, some Maine residents needed to drive with their headlights on during the day because the air was so thick from smoke. The drought has been especially difficult on the farmers. ''This is the driest I can remember,'' says Louis Borrilli, a North Haven, Conn., farmer who expects to lose 50 percent of his parsley, tomatoes, cucumbers, and squash. Across New York state the drought will result in smaller apples and onions, reports Mark Emery, direct of communications for the New York farm bureau. In addition, dairy farmers report lower yields on their hay and feed corn, which could have an impact on milk production this winter. The drought is also raising concerns about the water supply in some areas. The New York City reservoir system is down to 66.8 percent of capacity, compared with a normal 83 percent. New York is now in a ''drought watch'' stage, which calls for voluntary cuts in usage. On Friday, Marilyn Gelber, commissioner of the Department of Environmental Protection said the city is beginning to plan for mandated water conservation. In mid-September, the State Drought Management Task Force will meet to decide if the area should move to a drought warning, which will start to mandate restrictions. The drinking-water situation is becoming difficult for Poughkeepsie N.Y., which gets its water from the Hudson River. Lack of rainfall has reduced the flow of fresh water down the Hudson. As a result, salt water is now within four miles of Poughkeepsie's intake pipes. ''We're not in a panic situation yet, but it is something we are keeping our eye on,'' Mike McKeon, a spokesman for the state Department of Environmental Conservation in Albany, N.Y. Despite the current dry conditions, Ms. Vreeland says the conditions could change if a hurricane were to move up the East Coast. ''We can't rule out the possibility in such an active year,'' she says. Even a hurricane in Florida might bring some moisture to the area if the conditions are right. A storm now would be welcomed by the region's firefighters.