As in 2017, Thunder Snow spent the winter in Dubai and began his third campaign by contesting all three rounds of the Al Maktoum Challenge series at Meydan.
In the first round over 1600 metres on 11 January he started favourite but came home second behind the eight-year-old gelding Heavy Metal.
On 8 February Thunder Snow and Heavy Metal started joint-favourites for the second round over 1900 metres.
Thunder Snow raced in mid-division before making a forward move in the straight, and overtook the front-running North America 100 metres from the finish to win by a neck with Heavy Metal four lengths back in third.
The colt started odds-on favourite for the third round of the challenge over 2000 metres on 10 March, but was beaten into second by North America, who led from the start.

On 31 March, Thunder Snow was one of ten horses to contest the 23rd running of the Dubai World Cup and started at odds of 8/1.
The race featured a strong contingent from the United States comprising West Coast (the 5/4 favourite), Forever Unbridled, Gunnevera, Mubtaahij (Awesome Again Stakes) and Pavel (Smarty Jones Stakes).
North America was again in opposition while the other runners included Talismanic and the Japanese entrant Awardee.
Despite being drawn on the far outside, Thunder Snow went to the front soon after the start.
He set a steady pace before accelerating on the final turn and drew away from his rivals in the straight to come home five and three quarter lengths clear of West Coast, with Mubtaahij a neck away in third place.
Christophe Soumillon commented "I never thought I would be making the running, but no horses challenged early in the race.
West Coast let me go.
I was really cantering on the back straight and when I pushed him he kept finding".

After a break of four and a half months, Thunder Snow returned to European turf for the International Stakes at York Racecourse on 22 August.
Starting a 16/1 outsider he led the field into the straight but faded in the last quarter mile and came home last of the eight runners, more than 13 lengths behind the winner Roaring Lion.
In September the horse was sent to the United States to contest the Jockey Club Gold Cup over ten furlongs on dirt at Belmont Park.
After racing in third place behind Diversify and Mendelssohn he took the lead in the straight but was overtaken in the final strides and beaten a neck by the 46/1 outsider Discreet Lover.
On 3 November Thunder Snow was back in the United States for the Breeders' Cup Classic at Churchill Downs on 3 November and started at odds of 12/1 in a fourteen-runner field.
After tracking the leaders he moved up on the inside to take second place in the straight and kept on under a hard ride from Christophe Soumillon to finish third behind Accelerate and Gunnevera, beaten less than two lengths by the winner.

In the 2018 World's Best Racehorse Rankings Thunder Snow's rating of 122 made him the 20th best racehorse in world.
As in 2017, Thunder Snow spent the winter in Dubai and began his third campaign by contesting all three rounds of the Al Maktoum Challenge series at Meydan. In the first round over 1600 metres on 11 January he started favourite but came home second behind the eight-year-old gelding Heavy Metal. On 8 February Thunder Snow and Heavy Metal started joint-favourites for the second round over 1900 metres. Thunder Snow raced in mid-division before making a forward move in the straight, and overtook the front-running North America 100 metres from the finish to win by a neck with Heavy Metal four lengths back in third. The colt started odds-on favourite for the third round of the challenge over 2000 metres on 10 March, but was beaten into second by North America, who led from the start.
On 31 March, Thunder Snow was one of ten horses to contest the 23rd running of the Dubai World Cup and started at odds of 8/1. The race featured a strong contingent from the United States comprising West Coast (the 5/4 favourite), Forever Unbridled, Gunnevera, Mubtaahij (Awesome Again Stakes) and Pavel (Smarty Jones Stakes). North America was again in opposition while the other runners included Talismanic and the Japanese entrant Awardee. Despite being drawn on the far outside, Thunder Snow went to the front soon after the start. He set a steady pace before accelerating on the final turn and drew away from his rivals in the straight to come home five and three quarter lengths clear of West Coast, with Mubtaahij a neck away in third place. Christophe Soumillon commented "I never thought I would be making the running, but no horses challenged early in the race. West Coast let me go. I was really cantering on the back straight and when I pushed him he kept finding".
After a break of four and a half months, Thunder Snow returned to European turf for the International Stakes at York Racecourse on 22 August. Starting a 16/1 outsider he led the field into the straight but faded in the last quarter mile and came home last of the eight runners, more than 13 lengths behind the winner Roaring Lion. In September the horse was sent to the United States to contest the Jockey Club Gold Cup over ten furlongs on dirt at Belmont Park. After racing in third place behind Diversify and Mendelssohn he took the lead in the straight but was overtaken in the final strides and beaten a neck by the 46/1 outsider Discreet Lover. On 3 November Thunder Snow was back in the United States for the Breeders' Cup Classic at Churchill Downs on 3 November and started at odds of 12/1 in a fourteen-runner field. After tracking the leaders he moved up on the inside to take second place in the straight and kept on under a hard ride from Christophe Soumillon to finish third behind Accelerate and Gunnevera, beaten less than two lengths by the winner.
In the 2018 World's Best Racehorse Rankings Thunder Snow's rating of 122 made him the 20th best racehorse in world.
Thunder Snow