WATCH: The Prince and Princess of Wales arrive in Boston
After landing in the US, Prince William said: "Catherine and I are delighted to be back in the United States and are extremely grateful to Governor Baker and The First Lady of Massachusetts for their warm welcome into Boston.
"On this, our first overseas visit since the death of my grandmother, I would like to thank the people of Massachusetts and particularly of Boston for their many tributes paid to the late Queen. She remembered her 1976 bicentennial visit with great fondness.
The royal couple appeared in high spirits
"My grandmother was one of life's optimists. And so am I. That is why last year we launched the Earthshot Prize with the ambition to create a truly global platform to inspire hope and urgent optimism as we look to save the future of our planet.
"To the people of Boston, thank you. I'm so grateful to you for allowing us to host the second year of the Earthshot prize in your great city. Catherine and I can’t wait to meet many of you in the days ahead."
William and Kate flew with British Airways
In lieu of a private jett, the royal couple boarded a commercial British Airways flight from London to Logan International Airport. And according to fellow passengers, William and Kate were "utterly delightful".
Prince William and Princess Kate flew into Logan International Airport
Dressed to impress, the mother-of-three opted for a flattering deep purple suit which she teamed with a stylish turtleneck. Princess Kate elevated her outfit with a pair of matching heels and a dazzling pair of statement earrings.
Prince William, meanwhile, looked particularly dapper in a dark suit and navy tie.
During their royal tour, the royal couple will visit the John F Kennedy Presidential Library and Museum with Caroline Kennedy, the late president's daughter.
They will also learn about the work local organisations are doing to mitigate the risk of rising sea levels to Boston, and when they tour the Greentown Labs, in the nearby town of Somerville, they will get an insight into the development of innovative green technologies.
The mum-of-three opted for an aubergine-hued suit
At the premises of Roca, a non-profit organisation supporting disadvantaged young people, they will hear about the issues they face and Kate, who launched the Royal Foundation Centre for Early Childhood in 2021, will visit the Centre on the Developing Child at Harvard University.
Princess Kate looked radiant
The royal couple kicked off their royal tour at Boston City Hall on Wednesday evening where they met with Boston's Mayor, Michelle Wu. The duo were greeted with cheers from the crowds as they took to the stage.
Prince William delivered a brilliant speech before switching on vibrant green lights lighting up City Hall and other prominent buildings.
Addressing the crowds, William said: "May I say thank you to all the hardy Bostonians braving the rain this evening. Catherine and I are absolutely delighted to be with you today for our first engagement in the great city of Boston, as we start the countdown to The Earthshot Prize awards this Friday."
Princess Kate slipped into a Burberry dress
Whilst on tour, the royal couple will be supported by a whole team of people to ensure the smooth-running of their trip. From Kate's personal hairdresser and stylist to the couple's private secretaries and press officers, the couple's entourage plays a big part in the success of every tour.
The royal duo helped switch on the green lights
The last time Prince William and Princess Kate visited the United States was in November 2014, when they were guests of then-President Barack Obama at the White House.
Meanwhile, among those presenting the Earthshot Prize awards are the Oscar-winning actor Rami Malek, Home Alone and Schitt’s Creek star Catherine O'Hara and environmental activist and Big Little Lies star Shailene Woodley.
Sir David Attenborough attended the inaugural Earthshot Prize awards ceremony
Earthshot Prize council members Sir David Attenborough and Cate Blanchett will both provide voiceovers during the ceremony, which will be presented by UK broadcaster Clara Amfo and US actor Daniel Dae Kim.
Fans waited out in the rain
A royal source told HELLO!: "The prize has become the Prince's Superbowl moment of the year, and he looks forward to continuing to use the platform each year to shine a light on some of the most impactful projects doing amazing things around the world to save our planet's future."
Royal watchers awaiting the arrival of Prince William and Kate
William described the finalists as "innovators, leaders, and visionaries" and said they proved there are "many reasons to be optimistic about the future of our planet".
Eager royal fans gathered outside the City Hall Plaza
He went on to say: "They are directing their time, energy, and talent towards bold solutions with the power to not only solve our planet's greatest environmental challenges, but to create healthier, more prosperous, and more sustainable communities for generations to come".
Make sure you never miss a ROYAL story! Sign up to The Royal Explainer newsletter to receive your weekly dose of royal features and other exclusive content straight to your inbox.