Glen Boss will chase a hat-trick of wins in the Coolmore Classic after answering a call to partner in-form Victorian mare Jamaican Rain.

Boss, who is riding in Singapore, was sounded out by Richard Laming after the the Victorian trainer was struggling to find a rider for the lightly raced six-year-old at 52.5kg.

"I tried a few riders locally and a lot of them can't make the weight," Laming said.

"I know Glen is a big-race rider, he can make the weight, he thrives on the big races and he's ridden a lot of big-race winners at Rosehill.

"He knows the track like the back of his hand so I rang him up, he said 'let me have a look at her' and then he rang me back and said I'd love to come and ride her'."

Boss, who is seventh on the Singapore jockeys' premiership, has won the Coolmore Classic twice on Typhoon Tracy in 2009 and Aloha two years later.

He is making the trek to Sydney for one ride while Jamaican Rain has already tackled the road trip from her Cranbourne base, arriving in Sydney on Thursday.

Laming is hoping the forecast rain is right.

Jamaican Rain has been almost unbeatable on rain-affected tracks winning five of six starts on wet ground, including the Glasshouse Handicap at the Sunshine Coast in June.

Laming said the mare had improved since her first-up win in the Mannerism Stakes at Caulfield last month and was ready for her first test at Group One level.

"Although she has won on hard tracks she can really quicken on a heavy track which some horses can't do, but she can," Laming said.

"If the rain comes it's really going to help her chances. The mare is spot-on, she just keeps improving and she's improved since her first-up win.

"Her work has been absolutely A-1, she's tightened right up and she's right where we want her to be heading into a Group One."

At $8, Jamaican Rain is one of only two horses at single-figure odds for the Coolmore Classic with the Chris Waller-trained I Am Serious a $5.50 favourite.

Daysee Doom is $21 to defend her Coolmore Classic title and, along with stablemate Dixie Blossoms, will bid to give trainer Ron Quinton his fourth win in the race in the past eight years.

Quinton, who won the race twice as a jockey, also celebrated wins with Ofcourseican (2012) and Peeping (2016).