Mesonet Meteograms

A meteogram is a graph that shows how several meteorological variables change over time. The variables shown usually are temperature, dew-point temperature, and atmospheric pressure. In some cases the wind speed and direction are also displayed. The dew-point temperature is measure of the amount of humidity, or water vapor content, in the atmosphere. Its formal definition is as follows: the temperature to which the air must be cooled for dew to form. An example of dew formation is the condensation you will see on a cold glass of water. On the "Building Weather Instruments" page you can make your own hygrometer, or humidity measuring device, using this principle. When you are outside in higher humidity, condensation forms more quickly on your glass than when you are inside a drier, air-conditioned building. When the air is dry, it takes a lot of cooling before dew will form. In other words the dew-point temperature will be low. A high dew-point temperature means that there is a lot of moisture in the air and not much cooling will be required for dew to form. During rainy conditions, the humidity is high and the temperature and dew-point temperature will be almost the same. Also, rainy weather systems are usually associated with low pressure. Therefore, a meteogram is a useful tool to see if weather systems are approaching. Several activities to learn how to diagnose approaching fronts using meteograms can be found on the "What are Weather Fronts?" page.

Station:  Variable:  Units:  Date:  Scale:    


The meteogram above shows the changing temperature (red line), dew-point temperature (blue line), and pressure (green line) over a 24-hour timespan. Temperature units (for both dew-point and regular temperature) are shown on the left vertical axis, while pressure units are shown on the right vertical axis. Time is shown on the horizontal axis. You can select the end date and time of the meteogram. In other words, your meteogram will begin 24 hours prior to that end date and time. You can also select a Mesonet station of your choice and whether you want English or metric units.