With only six days left to buy tickets for the Nenana Ice Classic, the ice on the Tanana River at Nenana this year is as thin as it's been in years and all odds point to an early breakup, despite what has been a cold spring so far.

Whether that's the case is anybody's guess, which is what Alaska's richest guessing game is all about.

Each year, thousands of residents across the state pay $2.50 a ticket for the privilege of guessing exactly what time to the minute a wooden tripod erected on the Tanana River at Nenana will move downriver and stop a clock it is wired to on shore.

Last year, a pool of 19 winners shared a $301,000 jackpot in Alaska's version of a lottery when the ice went out at 6:22 p.m. AST on April 29.

The ice was 35 inches thick when officials measured it on Monday, the thinnest measurement for this date since 1998. Last year, the ice was 47.5 inches on March 30.

"It's staying pretty thin," Ice Classic manager Cherrie Forness reported by phone from the small Parks Highway community of Nenana, where the ice's thickness will be the main topic of conversation among the town's 350 residents over the next month.

"We've got a lot more snow this year and the ice is insulated with all the snow on top of it. I think that's why it's so thin."

The ice grows each year over the course of the winter, usually reaching its peak in late March or early April, Forness said. The average thickness on April 1 is 42 inches.

While anything under 40 inches is considered thin at this point, the ice didn't even make it to 40 inches this year. The thickest measurement so far is 37.5 inches on Feb. 25. A week later, the measurement dropped to 25 inches but the ice had inched its way back up to 35 inches over the past month.

Ice measurements are taken twice a week and holes are drilled in a different spot each time.

While there are no sure bets in the Ice Classic, the thinner the ice is at this point, the earlier the breakup is. Years with similar ice depths to this one have produced early breakups.

In 1998, the ice measured 34.5 inches on March 30 and it went out on April 20, the earliest date the ice has gone out in 87 years. In 1993, a year in which the ice never reached 30 inches, it went out on April 23, the second-earliest breakup date on record. The ice measured 28 inches on March 31 that year. In 1995, the ice was 34 inches on March 31 and it went out on April 26. In 1990, the ice was 36 inches on March 30 and it went out on April 24.

Any breakup prior to April 29 is considered early, Forness said. In 87 years, the ice has gone out only nine times before that date. The date that breakup has occurred most often is April 30. The ice has gone out nine times on that date.

Fairbanks Daily News-Miner