(Bloomberg) -- Volatility in arabica coffee futures is soaring as rapidly shifting weather in top grower Brazil and a focus on depleted stockpiles drives sharp price swings for the high-end beans.

The most-active futures contract rose as much as 4.1% in intraday trading Monday, rebounding after two days of declines. The 30-day price volatility is now the widest since late February.

After a week of hot, dry weather when temperatures neared 40C (104F) in key producing regions, rains are spreading again in Brazil. Normally, the moisture would offer some relief, but the new weather pattern has brought the threat of battering storms. Brazil’s National Institute of Meteorology has issued an alert for flooding, wind gusts and hail, which may affect some key coffee-producing municipalities in the state of Minas Gerais. 

Related: Parched Fields Are Threatening Even Next Year’s Crops in Brazil

Meanwhile, coffee traders trying to understand the market’s next moves are watching for shifts in inventory levels. Certified stockpiles have been plummeting, perhaps in advance of a Dec. 1 rule change that will prohibit sellers from pulling their older beans off the exchange and resubmitting them for a new round of certification to make them appear fresher. But more beans are now in line waiting to be graded, signaling the inventory levels are going to start to climb again. As of Friday, there were 14,675 bags pending grading, compared to 7,550 the previous day.

“As the certified stockpiles begin to rise, it is probably an indication that levels are close to a bottom,” said Hernando de la Roche, a senior vice president at StoneX Financial Inc. Some of the beans pending grading are coming from Africa, he said, meaning an influx from more traditional sources like Honduras and Brazil is probably still coming.

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