If Cramer is right about a sell-off coming early on Thursday, then that could be “your dream come true” to buy gold.

See, according to US Global Investors—“the best source on gold that I know of,” Cramer said—the gold stocks have jumped an average of 8.34% each September for the past 17 years, making right now a great time to buy in.

Investors always want at least some gold exposure in their portfolios, as it protects against inflation and overall market instability. But there’s another reason that Cramer’s bullish on the precious metal right now: scarcity.

Most of the world’s gold reserves have already been discovered. That’s why Kinross Gold was willing to pay $7 billion for RedBack, a gold company with mines in Western Africa. The same West Africa that is home to Mauritania, Cramer said, which has endured two coups in the last five years and human slavery is still in widespread practice. Most likely Kinross would never risk such an area if gold could be found anywhere else.

And believe it or not, but that $7 billion Kinross is paying might not be enough. Cramer said there is speculation that even higher bids are possible, which is another sign that gold is scarce.

So how do you play it? In this order, Cramer said: the SPDR Gold Shares ETF , gold coins, bullion (if you can afford the depository bank) and high-quality stocks like Agnico-Eagle Mines .

This confluence of events—the scarcity, seasonality—as well as what Cramer sees as a growing demand for gold by the middle classes of developing nations like China and India, could push the price per ounce to $1,300 in September, he said. That’s up from $1,190 where it closed today, a sizable jump for anyone who wants to play the trend.

“I think the clock is ticking before gold's next big run,” Cramer said. “Use tomorrow’s pending ugliness to buy some if you haven't already.”

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