Maritime Tropical Air Mass Brings Summer Storms over Sonora Desert

Canadian Tundra is Source Region for Cold Dry Air Masses

Cold, Dry Air

from Canada

Brings

Frigid Winter Air

to the United States

Air-MassSource RegionsforNorth America

Air Masses Acquire the Temperature and Moisture Properties

of their Source Regions

Lake-Effect Snow Belts

Lake-Effect Snow

cP Air-Mass Modified As It Crosses the Ocean

Cumulus Clouds Developing when mT Air from the Gulf of MexicoMoves over Heated Land in the Summer

Average AnnualPrecipitationin Eastern two-thirdsof the United States

Monthly Precipitation Data for Tucson, Arizona;Summer Precipitation Results from MonsoonCaused by mT Air Mass from the Pacific Ocean

Temperatures and Dew-Points at Weather Stations in the United States

Surface

Weather Map

during 1989

Cold Wave

Caused

by cA Air

Even ModernFrost-Prevention MethodsMay Not Be Able to Save Florida Citrus Cropsduring Cold Waves

A Record 69 Inches of Lake-Effect Snow Fell in Chardon, OH in 1996

Snow Totalsfrom 1996Lake-Effect Storm