The market's most widely watched fear gauge skyrocketed to a 2015 high Friday, indicating that investors are paying dearly for protection as stocks drop.
The CBOE Volatility Index, known as the VIX, has doubled in August. If it finishes the month here, it would log the largest monthly gain ever (using data going back 1990). That beats out the 91 percent advance seen in September 2008.
It is worth noting that the jump comes off of strikingly low levels. Just two weeks ago, the VIX hit a one-year low, as the S&P 500 traded in a remarkably tight range over the past several months.
That range was broken dramatically to the downside this week, as the large-cap index fell nearly 5 percent in just three sessions.
The VIX tracks the prices of options on the S&P 500. It is commonly known as the market's "fear gauge," since options are more commonly used to hedge risk than to speculate on upside.