GRAINS-U.S. wheat, corn, soy climb as MGEX spring wheat tops $8

* Adverse weather threatens U.S. spring wheat output

* Corn higher on U.S. Midwest weather uncertainty

* Soybeans up on weather worries, fund short-covering

(New throughout; updates prices, adds quotes, changes byline, changes dateline from previous PARIS/SYDNEY) CHICAGO, July 3 (Reuters) - U.S. wheat, soybean and corn futures rose in an abbreviated session ahead of the July Fourth holiday, buoyed by worries that hot and dry weather in the northern Plains spring wheat belt could spread into the western Midwest, analysts said on Friday. Spring wheat futures on the Minneapolis Grain Exchange (MGEX) soared to a four-year high above $8 a bushel. "The market has reawakened to weather risk. It started with wheat, and now it has caught up with the beans and the corn," said Terry Linn, analyst with Linn & Associates. At the Chicago Board of Trade, September wheat settled up 29 cents at $5.55 per bushel while front-month July, which expires next week, touched $5.39, the highest spot price since July 20, 2015. MGEX July spring wheat settled at $8.12 per bushel after reaching $8.16-1/4, its highest spot price since July 2013. Hot and dry conditions are forecast to intensify in the northern Plains spring wheat belt. Temperatures could top 100 degrees Fahrenheit (38 degrees Celsius) this weekend and early next week in Montana and western North Dakota, said Don Keeney with MDA Weather Services. "It's not good for the spring wheat at all," Keeney said, adding that forecasts were "bone dry" for the region after this week. CBOT September corn ended up 7-1/2 cents at $3.88-1/2 per bushel while August soybeans finished up 23 cents at $9.70 a bushel. Much-needed rains were expected in the Midwest this week, favoring central and eastern portions of the Corn Belt. But traders remained wary, especially given drier outlooks for the following week. "These rains of late have not had the coverage that has been forecasted. In particular there are concerns with the dryness in central Illinois," Linn said. Illinois was the second-largest U.S. corn producer last year and the top soybean grower. Soybeans appeared to draw support from fund-driven buying after supplemental data released by the U.S. Commodity Futures Trading Commission late Friday showed large speculators expanded their net short position in CBOT soybeans in the week to June 27 to a record-large 146,696 contracts. U.S. markets including CBOT grains and soy will be closed on Tuesday for the Fourth of July holiday. Trade is scheduled to resume Wednesday at 8:30 a.m. CDT (1330 GMT).

CBOT settlement prices:

Net Pct Volume

Last change change

CBOT wheat WU7 555.00 29.00 5.5 147621 CBOT corn CU7 388.50 7.50 2.0 185528 CBOT soybeans SQ7 970.00 23.00 2.4 65175 CBOT soymeal SMQ7 313.80 7.60 2.5 25646 CBOT soyoil BOQ7 33.24 0.20 0.6 24139

NOTE: CBOT September wheat, September corn and August soybeans shown in cents per bushel, August soymeal in dollars per short ton and August soyoil in cents per lb.

(Additional reporting by Sybille de La Hamaide in Paris, Colin Packham in Sydney and Naveen Thukral in Singapore; Editing by Marguerita Choy and Susan Thomas)