Weather Alerts for New York

This map shows recent moisture content over North America. Bright and colored areas show high moisture (ie, clouds); brown indicates very little moisture present; black indicates no moisture.

Weather Topic: What is Rain?

Home - Education - Precipitation - Rain

Rain Next Topic: Shelf Clouds

Precipitation in the form of water droplets is called rain. Rain generally has a tendency to fall with less intensity over a greater period of time, and when rainfall is more severe it is usually less sustained.

Rain is the most common form of precipitation and happens with greater frequency depending on the season and regional influences. Cities have been shown to have an observable effect on rainfall, due to an effect called the urban heat island. Compared to upwind, monthly rainfall between twenty and forty miles downwind of cities is 30% greater.

Next Topic: Shelf Clouds

Weather Topic: What is Sleet?

Home - Education - Precipitation - Sleet

Sleet Next Topic: Snow

Sleet is a form of precipitation in which small ice pellets are the primary components. These ice pellets are smaller and more translucent than hailstones, and harder than graupel. Sleet is caused by specific atmospheric conditions and therefore typically doesn't last for extended periods of time.

The condition which leads to sleet formation requires a warmer body of air to be wedged in between two sub-freezing bodies of air. When snow falls through a warmer layer of air it melts, and as it falls through the next sub-freezing body of air it freezes again, forming ice pellets known as sleet. In some cases, water droplets don't have time to freeze before reaching the surface and the result is freezing rain.

Next Topic: Snow