At 12:11 a.m. on Sunday, the National Weather Service issued an updated flash flood warning for Allegheny and Washington counties.

"At 11:22 p.m., emergency management and the public reported flash flooding due to thunderstorms that produced heavy rain across the warned area. Between 1 and 4 inches of rain have fallen. Flooding impacts will continue, but slowly subside as little to no additional rainfall is expected," says the weather service. "Flash flooding of small creeks and streams, urban areas, highways, streets and underpasses as well as other poor drainage and low-lying areas."

Locations impacted by the warning include Pittsburgh, Mount Lebanon, Bethel Park, McMurray, Washington, Canonsburg, Gastonville, West Mifflin, Baldwin, Upper St. Clair, Scott Township, Whitehall, South Park Township, Robinson Township, Cecil-Bishop, Jefferson Hills, Brentwood, Dormont, Castle Shannon and Pleasant Hills.

According to the weather service, "Turn around, don't drown when encountering flooded roads. Most flood deaths occur in vehicles. Be especially cautious at night when it is harder to recognize the dangers of flooding. Be aware of your surroundings and do not drive on flooded roads."

Your guide to weather alerts: advisories, watches, and warnings

A flash flood warning is issued when a flash flood is either imminent or already occurring. In flood-prone areas, it's crucial to move immediately to higher ground. A flash flood is a sudden and violent inundation that can develop within minutes to hours, and it can even happen in areas not currently experiencing rainfall.

A flood warning is issued when flooding is imminent or occurring.

A flood advisory is released when flooding is not expected to reach a severity level necessitating a warning. Nonetheless, it can still cause considerable inconvenience and, without exercising caution, potentially lead to situations that threaten life and/or property.

A flood watch is issued when conditions are favorable for flooding. It does not mean flooding will occur, but it is possible.

Staying safe during a flood: Recommendations from the weather service

If you're in a flood-prone area, or if you're camping in a low-lying spot, move to higher ground as a first step.

If local authorities issue an evacuation order, heed it promptly. Prior to leaving, secure your home by locking it.

If time allows, disconnect your utilities and appliances. This reduces the risk of electrical hazards during flooding.

Avoid basements or rooms submerged in water with electrical outlets or cords. Preventing electrical accidents is crucial.

If you notice sparks or hear buzzing, crackling, snapping, or popping noises, evacuate immediately. Avoid any water that may be charged with electricity.

Never attempt to walk through floodwaters. Even just 6 inches of swiftly moving water can forcefully knock you off your feet.

In the event you become trapped by moving water, make your way to the highest point available and contact emergency services by calling 911.

During heavy rain, flooding is possible, especially in low-lying and flood-prone areas. Never drive through water on the road, even if it does not appear to be deep. It takes just 12 inches of rushing water to carry away most cars, according to the weather service. Stay safe by being prepared and informed.

Navigating heavy rain: Essential safety measures for wet roads

During heavy rain, avoid parking or walking near culverts or drainage ditches, where swift-moving water can pose a serious risk.

Use the two-second rule to maintain a safe distance from the car in front of you and allow an extra two seconds in heavy rain.

If it is raining and the roads are wet, slow down. Take your foot off the accelerator and let your speed drop gradually. Never use the brakes suddenly because this may cause the car to skid.

Stick to the middle lanes to minimize the risk of hydroplaning. Outer lanes are more prone to accumulating water.

Enhance your visibility in heavy rain by turning on your headlights. Watch out for vehicles in blind spots, as rain-smeared windows can obscure them.

The first half-hour of rain is when roads are slickest due to a mix of rain, grime, and oil. Exercise heightened caution during this period.

Large trucks and buses can reduce your visibility with tire spray. Avoid tailgating and pass them swiftly and safely.

Your guide to weather alerts: advisories, watches, and warnings

A flash flood warning is issued when a flash flood is either imminent or already occurring. In flood-prone areas, it's crucial to move immediately to higher ground. A flash flood is a sudden and violent inundation that can develop within minutes to hours, and it can even happen in areas not currently experiencing rainfall.

A flood warning is issued when flooding is imminent or occurring.

A flood advisory is released when flooding is not expected to reach a severity level necessitating a warning. Nonetheless, it can still cause considerable inconvenience and, without exercising caution, potentially lead to situations that threaten life and/or property.

A flood watch is issued when conditions are favorable for flooding. It does not mean flooding will occur, but it is possible.

Staying safe during a flood: Recommendations from the weather service

If you're in a flood-prone area, or if you're camping in a low-lying spot, move to higher ground as a first step.

If local authorities issue an evacuation order, heed it promptly. Prior to leaving, secure your home by locking it.

If time allows, disconnect your utilities and appliances. This reduces the risk of electrical hazards during flooding.

Avoid basements or rooms submerged in water with electrical outlets or cords. Preventing electrical accidents is crucial.

If you notice sparks or hear buzzing, crackling, snapping, or popping noises, evacuate immediately. Avoid any water that may be charged with electricity.

Never attempt to walk through floodwaters. Even just 6 inches of swiftly moving water can forcefully knock you off your feet.

In the event you become trapped by moving water, make your way to the highest point available and contact emergency services by calling 911.

During heavy rain, flooding is possible, especially in low-lying and flood-prone areas. Never drive through water on the road, even if it does not appear to be deep. It takes just 12 inches of rushing water to carry away most cars, according to the weather service. Stay safe by being prepared and informed.

Navigating heavy rain: Essential safety measures for wet roads

During heavy rain, avoid parking or walking near culverts or drainage ditches, where swift-moving water can pose a serious risk.

Use the two-second rule to maintain a safe distance from the car in front of you and allow an extra two seconds in heavy rain.

If it is raining and the roads are wet, slow down. Take your foot off the accelerator and let your speed drop gradually. Never use the brakes suddenly because this may cause the car to skid.

Stick to the middle lanes to minimize the risk of hydroplaning. Outer lanes are more prone to accumulating water.

Enhance your visibility in heavy rain by turning on your headlights. Watch out for vehicles in blind spots, as rain-smeared windows can obscure them.

The first half-hour of rain is when roads are slickest due to a mix of rain, grime, and oil. Exercise heightened caution during this period.

Large trucks and buses can reduce your visibility with tire spray. Avoid tailgating and pass them swiftly and safely.