What does the weather code UP mean?

• A. Unidentified Precipitation
• B. Unidentified Pressure
• C. Unknown Precipitation
• D. Uncertain Precipitation

Answer: (A)

In weather observation codes, UP is used to indicate precipitation that has begun to fall but cannot be identified by the observer. This means something is precipitating, but the exact type—whether rain, snow, sleet, or something else—can’t be determined from the current observation. That clarity matters for forecasters and pilots, who need to know that precipitation is happening even if its form isn’t known yet.

So the best match is Unidentified Precipitation, because it directly describes precipitation whose type is not identifiable. The other options don’t fit the standard wording used in these codes—they either refer to pressure or use a different adjective that isn’t the label for this situation.