Warnings are once again in effect for heavy “super-fog” conditions Sunday morning.

The combination of smoke and water vapor is expected to be heaviest between 4 a.m. and 9 a.m. on Routes 13, 58 and 460 and adjacent secondary roads.

The smoke is the result of a wildfire burning in the Great Dismal Swamp National Wildlife Refuge. The fire’s size has not increased significantly in the past couple of days, holding steady at slightly more than 6,000 acres.

The Suffolk Police Department issued the following precautions for drivers traveling in the smoke:

• Slow down and turn your low-beam headlights on.
• Signal turns well in advance and brake early as you approach a stop. Remember that the vehicle behind you cannot see either.
• Keep your windshield and headlights clean.
• If you need to pull off the roadway, use the nearest exit rather than simply pulling to the side. If no exit is available, pull over as far as possible.
• Make sure everyone in the vehicle is buckled up or secured in a child safety seat.
• Delay your trip if possible.