NAIROBI (Reuters) - Kenya's weekly tea auction volumes dropped 33 percent to 18.5 million kg in January after violence hampered leaf picking and transportation, and bad weather could cut output in the year, the country's tea regulator said on Monday.

"The volume offered in 2008 declined largely due to the post-election disruptions and the effects of the current dry weather conditions in the tea growing areas and the frost effects in the West of Rift tea growing areas," the Tea Board of Kenya said.

"(The) weather forecast for the next month indicates that the long rains expected in mid-March may actually be received in mid-April," a statement by the board said.

Auction volumes in January 2007 stood at 27.8 million kg, said Sicily Kariuki, the board's managing director.

Associations grouping both estates and small holder sectors had reported that plucking, collection, processing and packaging were back to normal after weeks of violence following a disputed poll hurt operations. However, low rain over farms west of the Rift Valley was affecting production while frost conditions had also hit plantations in Nandi district and damaged 30 percent of tea yields in some cases.

Farms west of the Rift had reduced tea plucking days to three each week due to a low green leaf yield."

The board said weather forecasts now indicated that rain that was expected in mid-March could be delayed to mid-April.

"The amount and duration of the long rains has also been forecasted as lower than normal, therefore the expected high yields of April to May are unlikely to be attained," it said.