WABASH VALLEY (WTHI) - Accurate weather instruments are important to the Storm Team. But is your “at home” thermometer always correct? Accurate temperature data can be hard to come by. But the numbers the Storm Team uses in their graphics, are accurate because the data comes from thermometers in Stevenson Screens.
These screens are colored white so the screen reflects the sun's radiation. Just like a black-top road, black-colored outdoor surfaces tend to be much warmer than white-colored outdoor surfaces. Because darker-colored objects absorb that radiation from the sun.
These screens are typically 4 feet above the ground and the thermometer is placed inside the box to give us a very accurate measurement of the outdoor temperature.
Now your “at-home” thermometer likely has outside sources that influence the readings of the thermometer. So if your outdoor thermometer is hanging on the side of your house or in direct sunlight, the reading may be warmer than what it actually is.
Here's how to build your own Stevenson Screen:
The entire screen can be made of wood. You'll need screws, nails, a few corner braces, and 2 hinges.
It is important that the thermometer inside has plenty of ventilation. The thermometer should be at a level of 4 to 4.5 feet above the ground. The opening door should face north so that sunlight will not directly shine on the thermometer.
- 11.25" deep x
- 15.00" wide x
- 15.00" tall in back x
- 17.50" tall in front
The roof of the shelter should be sloped. The rooftop should be 16"x 23.5".
Floor slats are spaced 0.5" to 1" for ventilation. Louvered side panels and doors are preferred. But 1" thick panels drilled with several 1" holes slanted down toward the outside are adequate.
The back panel should be solid. And make sure all surfaces should are well painted white.
For more detailed instructions and pictures, go to www.weather.gov/rah/edu2.