When melting snow-crystals or raindrops fall through very cold air, they freeze to form small particles of ice, called sleet.

VOA: special.2011.01.11

During spring, warm air moves north and mixes with cold air remaining from winter.

VOA: special.2009.06.09

During the winter, breathing in cold air can trigger asthma symptoms.

VOA: special.2009.07.28

Finally,leave space between the food containers and the walls of the cold storage area so air can flow.

VOA: special.2009.11.30

Cold weather moves south and combines with the last of the warm air from summer.

VOA: special.2009.06.09