A girl wearing a Santa hat surfs at Bondi Beach on December 25, 2019 in Sydney, Australia. December is one of the hottest months of the year across Australia, with Christmas Day traditionally involving a trip to the beach and celebrations outdoors. (Photo by Mark Evans/Getty Images)

A person stands next to the skyline of lower Manhattan on the opening day the Edge NYC, an outdoor observation deck on the 100th floor of 30 Hudson Yards on March 11, 2020 in New York City. (Photo by Gary Hershorn/Getty Images)

Battersea Power Station Ice Rink in London, United Kingdom on November 13, 2022. Running until 8th Jan. 2023, a large outdoor ice-rink outside the power station and next to the riverside brings in festive Christmas fun with vivid illumination. (Photo by Guy Corbishley/Alamy Live News)

Visitors pass an exhibit for Sculpture by the Sea, along the coastal walk from Bondi to Tamarama in Sydney, Australia on October 24, 2025. The annual event is Australia’s largest annual outdoor sculpture exhibition. (Photo by Xinhua News Agency/Rex Features/Shutterstock)

Children play in an outdoor shower as a soldier takes part in a surprise operation in the Manguinhos slum in Rio de Janeiro, Brazil, Thursday, January 18, 2018. Troops have been sent to Rio due to the increase of the violence, and in an attempt to help restore order, but so far have had little impact. The operation on Thursday took place three weeks ahead of Carnival, when thousands of tourists are expected to arrive in the city. (Photo by Leo Correa/AP Photo)

An elderly man uses a fan to shade himself from the sun as he walks in a public park in Beijing, Tuesday, June 7, 2016. Thursday marks the Duanwu Festival, a public holiday in China celebrated with outdoor activities including dragon boat races. (Photo by Mark Schiefelbein/AP Photo)

Volunteers wearing face masks, gloves and protective gear to protect against coronavirus, gather to clean an area of an outdoor book market set up at Red Square with GUM, State Department store, left, St. Basil's Cathedral, center, Spasskaya Tower, second with, and the Kremlin Wall, right, in Moscow, Russia, Saturday, June 6, 2020. Muscovites clad in face masks and gloves ventured into Red Square for an outdoor book market, a small sign of the Russian capital's gradual efforts to open up amid coronavirus concerns. (Photo by Alexander Zemlianichenko/AP Photo)

Most pet cats will become timid or defensive when outdoors, but not Millie – after being adopted by her mountain-climbing owner Craig Armstrong, Millie has become a feline hiking and mountain-climbing legend.