rain-area

from The Century Dictionary.

• noun The region over which rain has fallen, shown on a daily weather-map.
• noun Any area over which rain is falling at any time.
• noun That quadrant of an extended cyclonic storm in which the most rain usually falls. It is the southeast quadrant in the storms of the United States, but the southwest quadrant in Europe, and a northerly quadrant in the storms of the southern hemisphere.
• noun That portion of the storm-area over which rain is falling, as distinguished from the portion over which snow is falling.