The manager of the Nenana Ice Classic says winners this year will split $300,000.
Cherrie Forness says ice on the Tanana River in Interior Alaska is "getting pretty rotten" and could go out at any time.
The Nenana Ice Classic is an annual game of chance in which participants guess the exact minute when river ice moves. Each guess costs $2.50.
A tripod is set up on river ice and tethered to a clock onshore. The winning moment occurs when the ice moves and the tripod wire trips the clock.
Ticket sales support the prize pool and Nenana charitable organizations.
Last year, 28 winners split a $330,000 jackpot.
April 20 is the earliest tripod has moved. May 20 is the latest date.
Nenana is 55 miles south of Fairbanks.