The National Weather Service issued a flash flood warning at 10:44 p.m. Saturday that is in effect until 12:45 a.m. Sunday for Northumberland and Union counties.

“At 10:44 p.m., Doppler radar indicated thunderstorms with heavy rainfall throughout the warning area. Between 1.5 and 2.5 inches of rain have fallen. Additional rainfall amounts of 1 to 2 inches are possible in the warning area. Flash flooding is underway or expected shortly,” the weather service explains. “Flash flooding in small streams and rivers, urban areas, highways, roads and underpasses, and other poorly drained and low-lying areas.”

Places affected by the warning include Sunbury, Milton, Lewisburg, Northumberland, Winfield, Linntown, New Columbia, Montandon, West Milton and Bucknell.

The weather service comments: “Turn back, don't drown if you come across flooded roads. Most flood deaths occur in vehicles. Be especially careful at night when flood dangers are harder to spot.”

Weather alert breakdown: advisories, observations and warnings

• Flash flood warning: take action!

A flash flood warning is issued when a flash flood is imminent or is already occurring. In areas at risk of flooding, it is important to get to higher ground immediately. A flash flood is a sudden and severe flood that can develop within minutes to hours and can occur even in areas where there is currently no rainfall.

• Flood warning: take action!

A flood warning is issued when flooding is imminent or already underway.

• Flood warning: Please note:

A Flood Warning is issued when flooding is not expected to reach a level of severity that would warrant a warning. However, such a warning may cause significant inconvenience and, if ignored, may result in situations threatening life and/or property.

• Flood warning: Be prepared:

A flood warning is issued when conditions are favourable for flooding. This does not mean that flooding will occur, but it is possible.

Coping with Floods: Weather Service Safety Guidelines for Weathering Storms

In flood-prone regions or when camping in low-lying areas, understanding and following the weather service's flood safety guidelines can be life-saving:

Move to higher ground:

If you are in a flood-prone area or camping in a low-lying area, the first step is to move to higher ground.

Follow the evacuation instructions:

If local authorities issue an evacuation order, obey it immediately. Secure your home by locking it before leaving.

Disconnect utilities and equipment:

If time permits, unplug your utilities and appliances. This will reduce the risk of electrical hazards during flooding.

Avoid flooded basements and flooded areas:

Avoid basements or rooms in contact with water where there are electrical outlets or cables. Preventing electrical accidents is crucial.

Fast evacuation for your safety:

If you notice sparks or hear buzzing, crackling, popping or banging noises, leave the area immediately. Avoid water that may be live.

Stay away from floods:

Never attempt to walk through flood water, even if it appears shallow. Even 6 inches of fast-flowing water can sweep you off your feet with full force.

If you are trapped, seek higher ground:

If you become trapped in running water, go to the highest possible point and call 911.

During heavy rain there is a risk of flooding, especially in low-lying or flood-prone areas. It is extremely important to never drive through water on the road, even if it does not appear to be deep. According to the weather service, as little as 30 cm of fast-moving water can sweep away most vehicles. Stay safe by being prepared and informed.

Driving on wet roads: Safety tips for wet weather

Heavy rains can cause flooding if they last for a long time or if there is excessive runoff. Excessive runoff can be due to saturated soil and/or rainfall intensity. Follow these weather service recommendations to stay safe during heavy rain:

Be careful with fast water flow:

Avoid parking or walking in close proximity to culverts or drainage ditches, as fast-flowing water may sweep you away during heavy rain.

Keep the safety distance:

In heavy rain, the two-second following rule is helpful. Increase it to four seconds to ensure a safe following distance in adverse conditions.

Reduce speed and drive carefully:

On wet roads, it is extremely important to slow down. Ease off the accelerator and avoid sudden braking to prevent skidding.

Choose your lane carefully:

Stay in the middle lanes as water often collects in the outside lanes.

Prioritize visibility:

Improve your visibility in heavy rain by turning on your headlights. Pay particular attention to vehicles in your blind spot, as rain-smeared windows can obscure them.

Be careful of slippery roads:

During the first half hour of rain, the roads are at their most slippery due to a mixture of rain, dirt and oil. Be especially careful during this time.

Keep a safe distance from large vehicles:

Do not drive too close behind large trucks or buses. The spray created by their large tires will limit your visibility. Also be careful when overtaking; if you must overtake, do so quickly and safely.

Pay attention to your windshield wipers:

• Overworked wiper blades can reduce visibility. If rain severely reduces your visibility, pull over to the side of the road and wait for conditions to improve. Seek shelter in rest areas or sheltered areas.
• If you can only stop at the side of the road, position your vehicle as far from the road as possible, ideally behind guard rails. Leave your headlights on and activate your hazard lights to alert other drivers to your position.

By following these safety measures, you can significantly reduce the risks and ensure your well-being during heavy rain. Stay informed about weather conditions and follow the advice of local authorities to ensure your trip is safe and unharmed.

Advance Local Weather Alerts is a service from United Robots that uses machine learning to compile the latest data from the National Weather Service.