The phrase "still warming up" is correct and usable in written English.
You can use it to describe the current status of something that is in the process of improving and has not yet reached its peak. For example, you could say "The economy is still warming up after the recession."
He is still warming up in his first proper job on a West End stage.
The Wong bun lands solid punches while the Ssam bun is still warming up, and easily takes the round.
It was Freundlich's wry way of telling his wife that in the photo the Knicks were still warming up and were not yet playing a game.
The Wong bun lands a few solid punches while the Ssam bun is still warming up, and easily takes the round.
The figurative subject matter is often clichéd but shows all three artists, who are still warming up in their careers, trying to expand from the merely pretty into something more serious.
As Arabic-speaking readers following the live video stream from Egypt's ON TV above will know, the satellite networks broadcasting the Egyptian presidential debate are still warming up for the candidates with a roundtable of newscasters discussing polls and other issues.
Bullet trains will flash on; flat panels will continue to shine; toilet seats will still warm up; factories will hum as they hummed before.
Even if humans stopped emitting greenhouse gases today, the earth would still warm up 0.5 degrees Fahrenheit over this century because of the already existing levels in the atmosphere.
Years later, the Surface tablet is still finding its feet in the tablet market, Windows Phone 8 is still just warming up, Windows 8 has been criticized by users and well, critics, and the Zune has completely ceased to exist.
But Ms. Flynn, a former critic for Entertainment Weekly, is still just warming up.
While independent jewelers may still be warming up to the men's fashion watch category, department stores are reporting strong growth in the segment.
