What Is Black Ice? — In Plain Words

General information only.

The short answer

The National Weather Service Glossary defines black ice this way:

“Slang reference to patchy ice on roadways or other transportation surfaces that cannot easily be seen.”

The same glossary page gives a second sense: “In hydrologic terms, transparent ice formed in rivers and lakes.”

This page is about the first sense — the ice on roads.

Why this page is short

The official National Weather Service pages on this exact term are short, so this page is short. It does not add tips, numbers, or explanations beyond what those pages state.

When it can form

The National Weather Service in Paducah says: “When recent rain or snowmelt comes into contact with freezing temperatures, black ice can form — and you might not even see it.”

Paducah also says: “And while black ice is more prevalent at night, it can often stick around for the morning commute.”

Why it is dangerous

It is hard to see. The glossary definition above says it “cannot easily be seen,” and Paducah says “you might not even see it.”

The National Weather Service in Amarillo puts it this way: “Roads which may appear clear in the wintertime may actually be coated with a thin layer of ice, commonly called black ice. This thin layer of ice can cause you to lose control of your vehicle.”

Bridges freeze first

The National Weather Service in Paducah says: “You’ve probably seen road signs advising that bridges freeze before roads, but do you know why? Having open air underneath the bridge means the cold air surrounds the bridge both above and below.”

Paducah adds: “If there’s even the chance that a bridge might be frozen, SLOW DOWN! And do it before you cross the bridge — changing speed on ice is dangerous.”

Driving guidance — the National Weather Service in Amarillo

Attribution: The guidance in this section is from the National Weather Service in Amarillo, from its “Winter Weather Safety” page, under “Vehicle Safety Tips.” It is printed here in that page's wording.

• Drive carefully and defensively.
• Instead of slamming your breaks, pump your breaks when trying to stop on snow or ice covered roads.
• Reduce your speed if you detect black ice.

Paducah's guidance, in its own words, is: “Use extreme caution when driving...don’t let black ice sneak up on you.”

General information only.