FM Radio station keeps shifting by itself

I wake up every morning with an FM alarm radio.
Sometimes, (it seams to happen on specific months during the year) when the alarm goes off at 7AM it is not quite on the channel so I adjust it. But at 7:30AM it goes off again. If I adjust the station at 7:30AM it will be ok the next day only at 7:30AM.
It's like the signal changes on different times of the day.

So far I have tried 3 radios and all had the same issues.

I would like to understand why this is happening and how I can fix it.

Thanks

Mike

Presumably these are cheap analogue radios?, they drift - end of story.

Get a radio with a digital tuner that stays locked on frequency.

As Nigel noted it's the radio, not the station. Many of the better old analog FM radios had AFC (Automatic Frequency Control) which was a feedback control circuit to keep the radio locked on the station. If the radio doesn't have that, it can drift off station with temperature change. Is the room temperature significantly different between when you set the station and the next morning?

I have an old radio alarm clock with no FM. It still works but on the odd occasion I use and set it to wake up to radio, mostly what I get is crackly music or just crackle. You have to buy a newer and probably better alarm clock.

Analog tuners with AFC will behave like the OP said. The local oscillator is drifting, but being held by the AutoMatic Frequency Control (AFC). Eventually the oscillator drifts so far that AFC can no longer hold it, so the tuning suddenly appears to snap to some dead air above or below the original station. Get a better radio...

Looks like there are not too many solutions, I guess it is clear, I will change the radio for a better one.

Thank you all for your responses,

Mike