The most common piece of equipment is the thermometer . a thermometer measures . the temperature of the air . by looking at it, people can tell exactly how hot or cold it is . another common instrument is the barometer . this measures the air pressure. so people can how if it is going to rain or not . usually , when the air pressure drops , bad weather is coming . and when it goes up , good weather is coming . there is other equipment , too. a rain gauge measures the amount of rain that has fallen in a place . and an anemometer is used to measure how fast the wind is blowing . it's really useful on windy days! and some people even have weather vanes on their homes . they show which direction the wind is blowing!