Showalter Index Calculator

Extreme Heat in the Central US Expands to the Southeast; Severe Weather & Flash Flooding Threats in the Plains & Upper Midwest Tonight.

Dangerous heat continues across portions of the Central and Southeast U.S. through July. Heavy rains, flooding, & severe weather are possible across the Plains & Upper Midwest to the upper Great Lakes tonight, with the heavy rain and flooding threat continuing through Friday. Tropical Depression 12W brings heavy rain to Guam & the Marianas through Saturday. Read More >

Showalter Index

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What does my answer mean?

Showalter Index greater than 0: Stable, but weak convection possible for SI = 1-2 if strong lifting is present.
Showalter Index between 0 and -3: Moderately unstable.
Showalter Index between -4 and -6: Very Unstable.
Showalter Index between less than -6: Extremely Unstable.

Extreme Heat in the Central US Expands to the Southeast; Severe Weather & Flash Flooding Threats in the Plains & Upper Midwest Tonight.

Showalter Index

by Tim Brice and Todd Hall

Enter the temperatures that you would like:

What does my answer mean?

What is the formula for the Showatler Index?