Thermometer

Thermometers measure the temperature.  As it warms up outside, the mercury in the thermometer expands and rises and vice versa.  The first thermometers were called thermoscopes.  The first inventor to put a numerical scale on this instrument was Santorio Santorio, and Italian Inventor.  Daniel Gabriel Fahrenheit invented the first alcohol thermometer in 1709 and the Fahrenheit Scale.  Anders Celsius created the Celsius scale, also known as the centigrade scale in 1742.  Lord William Thomson Kelvin created the Kelvin scale in 1848.

http://inventors.about.com/library/inventors/blthermometer.htm

Barometer

It measures air pressure.

Rain Gauge

It measures the amount of rainfall.

Anemometer

It is also known as a wind vane.  It measures the winds velocity.  There are three different kinds:  Mechanical, Hemispherical Cup, and Sonic.

http://inventors.about.com/od/astartinventions/a/Anemometer.htm

Hygrometer

It is used to measure the moisture content or humidity of air.  Some hygrometers use blonde human hair, electrical resistance, and the dry and wet bulb psychrometer.

Weather Balloon

They are made with latex or synthetic rubber and hold helium or hydrogen to lift.  A radiosonde, which is powered by a small battery, is attached to the balloon and measures pressure, temperature, and relative humidity.  As these balloons increase in height they expand form six feet to twenty feet in diameter.  They also send back the data to a piece of tracking equipment on the ground.  The meteorologists can also find the wind speed and direction by where the balloon is located.

http://www.srh.noaa.gov/epz/kids/balloon.shtml

Remote Sensing

There are three different kinds.  Satellites use light, the infrared scanners on satellites use heat, and Doppler radars use radio waves.

http://www.srh.noaa.gov/srh/jetstream/remote/remote_intro.htm