That’s because “Jeopardy!” defined sleet as “precipitation coming down as a mixture of snow and rain.” While sleet is often displayed on weather maps as a wintry mix of precipitation, it’s not a combination of multiple precipitation types. In fact, sleet is its own form of precipitation.
Snow ordinarily forms when temperatures are below freezing through the entire column of the atmosphere, allowing an ice crystal to develop and remain frozen during its entire journey to the surface. Most snowflakes are six-sided. The crystalline structure of snow allows it to stack up and accumulate more dramatically than any other type of precipitation.
Rain, meanwhile, is straightforward. Either temperatures are too warm anywhere to support snow and, subsequently, moisture remains in liquid form on the way down or air near the surface is sufficiently warm. In the latter case, precipitation could fall as snow and melt into ordinary raindrops on the way down.
Sleet forms differently. Precipitation starts as ice crystals but then begins to melt upon encountering a layer of milder air at the mid levels. It refreezes before hitting the ground, however, becoming a small pellet-like chunk of ice the size of a BB or small pea. Because sleet is solid ice rather than ice crystals, it doesn’t melt as quickly upon contact with a roadway or mild ground. That helps make for slicker travel, even if sleet doesn’t pile up as much as snow.
Adding to the assortment is freezing rain, which is, unsurprisingly, rain that falls as a liquid and ices up upon contact with a subfreezing ground.
All that to say sleet is not a mixture of rain and snow. Sleet can sometimes fall simultaneously with rain and snow in response to changing temperature profiles, signifying a transition between precipitation types, but sleet itself isn’t rain or snow. You can usually hear sleet pinging off the hood of your vehicles or pattering off a window. It sounds like a gentle confetti of ice cream sprinkles.
While we’re at it, don’t let anyone confuse you about the difference between sleet and graupel. The former is frozen water. The latter is a “soft” snow pellet, akin to a Dippin’ Dot, that’s been rimed in a thin glaze of ice stemming from supercooled water droplets.
And hail forms only in convective updrafts, or those associated with heavy showers or thunderstorms. Odds are you’ll never encounter bona fide hail in a winter storm. It results from strong upward motion in a cloud that suspends water droplets at subfreezing high altitudes.
So next time you hear someone describe sleet as a mix of snow and rain, don’t be afraid to drop some knowledge on them. After all, it’s a very hot topic.