Four elements of weather:
temperature, wind, snow or rain, and sunlight or clouds.
The tools used to measure them:
Thermometer for measuring air and sea surface temperature. Barometer for measuring atmospheric pressure. Hygrometer for measuring humidity. Anemometer for measuring wind speed.
Thermometer:
Celsius, Fahrenheit, Kelvin, Reaumur, and Rankine.
Barometer:
pounds per square inch, pascals and inches of mercury.
Hygrometer:
absolute, relative, and specific.
Anemometer:
feet per minute, or FPM