Relentless rains in recent weeks hurt the quality of some 420,000 tonnes of soy in Mato Grosso, the top-growing state's farm institute says. This is causing buyers to reject or purchase the grain at heavily discounted prices.

But rains largely eased off over the last five days, spurring intensive harvesting. Producer association Aprosoja says 30 percent of the crop has been harvested in Mato Grosso, compared with 12 percent nationwide.

"Between Feb. 20 and 24, rains will strengthen over the southeast and center-west," Somar said in a daily weather bulletin.

In the main central grain belt of Mato Grosso, 200 millimeters (8 inches) of rain have fallen since the start of February. The historical average for the entire month of February is 262 mm in the state.

While the center-west dries out, rains should fall over the weekend over southern producing states Rio Grande do Sul and Parana, where harvesting is just starting.

The following is a table of rainfall forecasts for the next five days over Brazil's main grain-producing states. The data, in millimeters, was provided by Somar, which specializes in forecasting weather for Brazil's crop regions.