The Magpies sealed a top-four finish in the Premier League with a 0-0 draw against Leicester on Monday (22.05.23) and will compete in Europe's top competition for the first time since 2003 next term.
Newcastle were in the relegation places when Howe took charge of the club in November 2021 and the coach did not expect a European push to materialise so quickly.
Howe told Sky Sports: "[Our expectation this term] certainly wasn't top four.
"I think you always hope, you always believe and you have to dream.
"But we didn't feel that we were ready for that. After last season's battle with relegation it was whether we could consolidate and become a better team.
"To not have that flirtation with relegation and try to give it a go, it's just been incredible."
Newcastle's fortunes have been boosted by the Saudi-backed owners who took charge in 2021 and Howe warned that the club must be "smart" in their recruitment this summer as they will have to cope with the demands of Champions League football.
He said: "We’ve got work to do, we’ve got work to do to be ready, we know that. There’s a big task ahead of us, but I’m confident we can do it.
"It’s going to be important for us, we have got to try to get it right and that’s going to underpin our success, really. I think we’ve been really, really good in the three transfer windows so far since I’ve been here.
"The challenge gets harder and more difficult because, now we’ve become a better team, there are fewer players who would make us better, so it’s going to be a big window for us.
"It won’t be huge numbers – I don’t think it can be. We don’t have the ability to spend the money that people will think we have, so we’re going to have to be smart."