Long has featured in West Brom's first three Premier League games this season, but is yet to open his account as the Baggies have failed to find the net in a poor start to the campaign.
Hull want to take advantage of Long being in the last year of his contract at The Hawthorns, with Tigers boss Steve Bruce granted permission to talk to the forward this evening, according to Sky Sports News.
The 26-year-old is currently on international duty ahead of World Cup qualifiers with Ireland but is thought to have left the team hotel for discussions over his future.
West Brom have an option to extend Long's contract by a further year, but have allowed Hull to talk the Ireland marksman ahead of tonight's 11pm transfer deadline.
Everton are also thought to be monitoring his progress, but have less than four hours to register a concrete enquiry.