After several days/weeks of meteogram observations, guide students to discover some of the following interrelationships among weather variables.

• Air pressure vs. cloud coverage

  (In general, low air pressure is associated with cloudiness and a chance of precipitation; high pressure is associated with fair weather and clear skies.)

   

• Usual time of daily high and low air temperature

  (The daily high temperature usually occurs sometime during the afternoon; the daily low temperature usually occurs just before sunrise.)

   

• Dew point depression (air temperature minus the dew point temperature) vs. cloud coverage &/or cloud height

  (In general, when the surface dew point depression is small, skies will be overcast and cloud bases close to the Earth's surface.)

   

• Wind direction vs. temperature

  (When the wind is coming from the north, air temperatures are usually cooler; southerly winds usually bring warmer temperatures. Along the East Coast of the U.S., easterly winds usually bring cooler air onshore during the Summer and warmer air onshore during the Winter.)

   

• Air temperature vs. type of precipitation

  (Winter is the perfect time for this observation! For snowfall to occur, the temperature of the atmosphere must be below freezing from top to bottom.)

   

• Air temperature vs. dew or frost

  (Dew forms when the air temperature is equal to or lower than the dew point temperature, and the dew point temperature is above freezing. Frost forms when the air temperature is equal to or lower than the dew point temperature, and the dew point temperature--technically called the frost point temperature--is below freezing.)

   

• Dew point (or frost point) vs. the overnight minimum temperature

  (Due to the release of latent heat energy as water vapor changes phase from gas to liquid or gas to solid, the overnight low temperature rarely drops below the dew point temperature.)

   

• Cloud height vs. precipitation

  (In general, precipitation is associated with low- to mid-level clouds.)

   

• Cloud coverage vs. the daily maximum and minimum air temperature

  (In general, there is a greater temperature range when skies are clear, and a smaller temperature range when skies are overcast.)

   

• Percent of sky coverage and cloud height

  (Overcast skies are often--but not always--associated with low-level clouds.)