Showalter Index Calculator

Severe Weather and Heavy Rainfall from the Midwest to the Ohio Valley; Mid-Summer Heat Continues

Severe thunderstorm and heavy rainfall threats will persist from the Midwest to Lower Great Lakes through Monday, shifting into the Ohio Valley and Central Appalachians Monday evening into Tuesday. Mid-summer heat will continue across much of the CONUS this week, with record highs possible well into the 100s across the south-central High Plains. 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.

Severe Weather and Heavy Rainfall from the Midwest to the Ohio Valley; Mid-Summer Heat Continues

Showalter Index

by Tim Brice and Todd Hall

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What is the formula for the Showatler Index?