The 25-year-old, however, continues to train with the English Championship club, who lost manager Simon Grayson to Sunderland on Thursday.
May played under Dons boss Derek McInnes when he came through the youth ranks with St Johnstone.
Preston bought May, who earned his only Scotland cap in a 2014 friendly with England, from Sheffield Wednesday for an undisclosed fee in September 2015.
The striker suffered a serious knee ligament injury that December and did not make his return to action until this February.
He went on to make 10 appearances, scoring once, as his side finished 11th in England's second tier.
May had previously spent a season with Wednesday after being signed from St Johnstone, scoring seven goals in 41 games.
The striker, who spent time on loan to Alloa Athletic and Hamilton Academical before breaking into Saints' first-team under McInnes, has a year left on his Preston contract.
Grayson had bolstered Preston's striking options this summer by paying compensation fees to Manchester United for 21-year-old Josh Harrop and to Cork City for Sean Maguire.
Veteran forward Jermaine Beckford was among the players released.
Aberdeen have added striker Greg Stewart on loan from Birmingham City and agreed a deal to sign attacking midfielder Shaun Maloney from Hull City after Jonny Hayes was sold to Celtic and forward Niall McGinn rejected a new contract.
Aberdeen have made a bid for Preston North End striker Stevie May.