Volatility Futures at Key Inflection Point After S&P 500 Rout

One marker of stock-market volatility is at a level that in the past has signaled the S&P 500 Index was close to a near-term bottom.

As equities slump globally, volatility is rising with investors snapping up options to protect from a further selloff after surprisingly weak jobs growth on Friday added to concern that the Federal Reserve is waiting too long to reduce interest rates. So much so that futures on the Cboe Volatility Index have inverted, a signal that the here-and-now uncertainty is higher than that further down the line.

August VIX contracts are trading at 24.4, compared with ...