Frantic Americans snapped up $1 lottery tickets on Tuesday as the Mega Millions jackpot swelled to $636 million, making it the second-richest lottery draw in US history.
Brisk sales were reported in the 43 states where Mega Millions is played -- and if no winner emerges by this weekend, the jackpot could potentially balloon to a staggering $1 billion on Christmas Eve.
"The jackpot has been rolling since it was last hit in Maryland for $190 million on October 1," said the Multi-State Lottery Association in a statement.
Drawings were scheduled for 11:00 pm Tuesday (0400 GMT Wednesday) and again on Friday at the same time.
The record jackpot of $656 million in March 2012 was split between ticket holders in Illinois, Kansas and Maryland, but this draw is the first since a rule change in October.
Previously, players picked five numbers from one to 56 plus a number from one to 46.
Now it's five numbers from one to 75 plus a number from one to 15 -- shifting the odds of winning from one in 176 million to one in 259 million.
By comparison, the odds of being struck by lightning in the United States in one's lifetime is one in 10,000, according to the National Weather Service.