Sept. 27 (Bloomberg) -- Cotton futures rose, capping the longest rally in seven weeks, on signs of lower global supplies.

Cotlook Ltd., a Birkenhead, England-based research company, cut its estimate on global production in the 12 months ending July 31 by 0.6 percent, reflecting “unhealthy weather” in China, the worldΆs biggest producer. Above-average rain next month in southern states of the U.S., the top exporter, will slow the harvest, Commodity Weather Group in Bethesda, Maryland, said this week. IndiaΆs monsoon exceeded the 50-year average.

“Recent rains in the U.S., China and now India are reminding traders that these generally late crops are still exposed to potentially harmful weather over the coming weeks,” Peter Egli, a Chicago-based risk manager at Plexus Cotton Ltd., said in a report.

Cotton for December delivery climbed 1.4 percent to settle at 86.63 cents a pound at 2:30 p.m. on ICE Futures U.S., the biggest increase since Aug. 16. The fiber capped the fourth straight gain, the longest rally since Aug. 8.