* Flooding in southern Brazil threatens soy, corn crop losses

* Wheat rallies on volatile weather in Russia

* USDA says U.S. corn crop 36% planted, soybeans 25% done

CHICAGO, May 6 (Reuters) - U.S. wheat, soybean and corn futures soared to multi-month highs on Monday on worries about potentially crop-damaging weather in Brazil and Russia.

Chicago Board of Trade (CBOT) July wheat settled up 26-1/4 cents at $6.48-3/4 a bushel after climbing to $6.50-1/4, its highest level since late December.

CBOT July corn ended up 8-3/4 cents at $4.69 a bushel, having reached its highest point since January, and July soybeans climbed 33-3/4 cents to finish at $12.48-3/4 a bushel, also reaching a four-month peak.

Wheat's rise was driven by volatile weather conditions in Russia, including dryness in the south of the country and May frosts in some areas.

Consultancy IKAR cut its forecast for the world's largest wheat exporter last week.

Meanwhile, the outlook for the soybean harvest in Brazil's Rio Grande do Sul state is deteriorating after torrential rains flooded fields, with about a quarter of beans left to harvest. The deluge may also reduce the state's corn volumes and further clip South American supply after downgrades to estimates of Argentina's crop.

Grain traders were monitoring corn and soybean planting progress in the U.S. Midwest amid bouts of adverse weather, said Bill Lapp, president of Advanced Economic Solutions.

Volatile weather stories were prompting fund activity, analysts said.

"We're starting to see the funds over the last few weeks start to flip out of their commodity deflation mode that they've been in for the last two years," said Arlan Suderman, chief commodities economist at StoneX.

"There were fundamental stories that were being ignored before that suddenly that markets are paying attention to," Suderman added.

After the CBOT close, the U.S. Department of Agriculture said the U.S. corn crop was 36% planted by Sunday, behind an average of trade expectations and lagging the five-year average of 39%. The USDA pegged soybean planting as 25% complete, behind trade expectations but still ahead of the five-year average of 21%.

The government rated 50% of the U.S. winter wheat crop in good to excellent condition, up from 49% a week ago, while the U.S. spring wheat crop was 47% planted, well ahead of the five-year average of 31%.

(Reporting by Renee Hickman; Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore Editing by Marguerita Choy and Will Dunham)