GRAINS-Wheat rises to one-month high, corn and soybeans also extend gains

PARIS/CANBERRA, May 21 (Reuters) - Chicago wheat futures extended gains on Wednesday to a one-month high, supported by a weaker dollar and short-covering encouraged by concerns over Northern Hemisphere production.

Corn continued to track strength in wheat as it reached a new one-week peak. Soybeans also rose to a near one-week high, supported by a rise in crude oil and fears that heavy rains may have damaged soy crops in Argentina.

The most active wheat contract on the Chicago Board of Trade (CBOT) Wv1 was up 0.5% at $5.48-3/4 a bushel at 1103 GMT, after reaching $5.51, its highest since April 23.

The contract had rallied 3.2% on Tuesday as an unexpected decline in U.S. wheat crop ratings and reports of adverse weather in China and Russia triggered short-covering by investors after prices hit a five-year low last week.

The gains were more modest on Wednesday, with traders and analysts cautioning that crop damage in China and Russia may be limited and overall Northern Hemisphere harvest prospects still favourable.

"The funds have been buying wheat for a week covering their large short position in July futures. Things accelerated yesterday after the market clearly broke above the 20-day moving average," Andrey Sizov, head of crop consultancy Sovecon said.

"At this stage I'm not sure that fundamentally recent news was such a big bullish story," he said.

Parts of China including the major wheat-producing region of Henan saw temperatures reach 40 degrees Celsius (104 degrees Fahrenheit) earlier this week, though traders said the heat did not appear to last long enough to pose a serious threat to crops.

In Russia, the world's biggest wheat-exporting country, traders believe that recent frosts have not caused significant damage either. A lack of rain is nonetheless expected to deplete the harvest in Rostov, Russia's largest grain region, the head of the local grain lobby group said.

CBOT soybeans Sv1 rose 0.7% to $10.60 a bushel and corn Cv1 ticked up 0.2% to $4.55-1/4 a bushel.

The U.S. dollar =USD weakened again on Wednesday after cautious remarks about the U.S. economy by Federal Reserve officials. USD/

A rise for crude oil LCOc1, after a report that Israel could be preparing to strike Iranian nuclear facilities, lent some support to oilseeds like soybeans, which are partly used to provide vegetable oil for biofuel. O/R