How to Read a Weather Thermometer

One of the most basic instruments in reading weather is the weather thermometer. The weather thermometer measures heat. The most common outside thermometer is the expansion thermometer, such as the mercury thermometer, which is much more accurate than other thermometers.

Things You'll Need

• Outdoor expansion thermometer

Instructions

1. The volume of liquid in the thermometer changes relative to the temperature. As the temperature rises, the liquid expands in the capillary tube. There are two different scales on most thermometers--Fahrenheit and Celsius.

2. The thermometer will be marked with lines. Each full degree will be represented by a full line, and each fraction of a degree will represented by a shorter line. On the Fahrenheit scale, the freezing point is 32 degrees, and the boiling point is 212 degrees. On the Celsius scale, the freezing point is 0 degrees, and the boiling point is 100 degrees.

3. Within the tube, there will be a red, silver or blue line. This is the liquid in the tube that expands when the heat rises. The line will stop somewhere along the scale. Where it stops is where the temperature should be read.

Tips & Warnings

• Placement of a thermometer is important. The thermometer needs exposure to airflow, but also needs to be sheltered from solar heating.

• Always wear gloves to clean up the pieces of a thermometer, should it break.

References

• Reach Out Michigan
• Weather Notebook