CANBERRA, March 13 (Reuters) - Cotton Australia on Wednesday raised its estimate for Australian production this year to "at least" 4.5 million bales after widespread rainfall boosted yields.

Unexpectedly plentiful rain across eastern and southern Australia in recent months has transformed the country's agricultural outlook after a long dry period last year that scorched crops and pastures.

Australia is one of the world's biggest cotton exporters. Its 2023/24 harvest is just beginning.

"Our growers were expecting a long, hot and dry summer forcing a crop revision below 4 million bales," said Adam Kay, CEO of Cotton Australia, an industry group.

"The rains across our largest growing areas were very welcome and now we are expecting at least 4.5 million bales which will result in more than $3.6 billion for the Australian economy," he said.

The U.S. Department of Agriculture (USDA) estimates Australian cotton production this year of 4.8 million bales, or 1.045 million tons. The Australian government this month forecast cotton production of 1 million tons.

The 2023/24 crop will be smaller than those of 2021/22 and 2022/23, which saw plentiful rain throughout the growing season, but significantly above the 10-year average.

Cotton Australia said close to 480,000 green hectares of cotton had been planted this season, mostly in New South Wales and Queensland states but also in the Northern Territory and Western Australia state.

U.S. cotton futures have risen sharply this year, with the USDA forecasting the lowest U.S. production in 40 years. (Reporting by Peter Hobson; Editing by Michael Perry)