Putting a pear tree outside

I've got a pear tree, poundstretcher job. I've potted it but it's still indoors, and leafing up now. Will I need to wait until the frosts have finished to put it out or can it go out sooner? I have a sheltered area it'll be in temporarily, but the frost does still touch a bit there.

 

Once its got leaves it will be damaged by frost.
Best to put it outside when no frost is threatened, but bring it in overnight should frost be forecast.