SAO PAULO/NEW YORK: A new polar air mass is set to move over Brazil’s agricultural areas this week, threatening further damage to coffee and sugar cane crops already hurt by strong frosts last week.

This would be the third cold wave to bring freezing conditions to Brazil’s Southeast farm belt this winter, something not seen in decades. Brazil has already been suffering through one of its worst droughts in 90 years, and dealing with transportation logistics delaying exports of key crops like coffee to various destinations.

July 20’s frosts were the strongest since 1994 and have already damaged up to 200,000 hectares (495,000 acres) of coffee fields. Arabica coffee futures rose nearly 10% on Monday after gaining almost 20% last week.

The air mass will reach southern Brazil by Wednesday, according to forecasters, then move to key planting areas in Sao Paulo and Minas Gerais states on Thursday and Friday.

“I’m not sure if the new cold wave is going to be as strong as the last, but it is a high pressure system. We do not rule out widespread frosts over areas of citrus, coffee and sugar cane,” said Marco Antonio dos Santos, a meteorologist at Rural Clima.

Brazil’s drought has already reduced prospects for several crops including coffee, sugar and corn.

Commodities broker Marex Spectrum said on Monday some sugar cane farms in Brazil had up to 35% of the fields damaged by frosts, though the general impact was smaller. Estimates for Brazil’s sugar production will likely come down, it added.

The cold could also affect next year’s cane and coffee crop.

“Once it (polar mass) is over southern Brazil it will be slow to move out. This could allow for multiple days of frost and freeze conditions in the coffee belt,” said independent meteorologist Mike Palmerino. He estimated minimum temperatures of -2 Celsius (28 Fahrenheit) on Thursday and -1 C on Friday.

“The dryness of the air and the persistence of cold high pressure at the surface will maximize the ability to produce damaging cold,” he added.