This is from a bit of an odd point in Thor history. The previous storyline, featuring Galactus, had wound up heavily modified (with several unused pages later showing up in portfolios and fanzines), and the original intention was for Thor to team-up with Galactus to fight the Thermal Man, who had been terrorizing New York while Thor's fellow Asgardian's tried to hold him back. This change in the status quo for Galactus was apparently not what Marvel wanted, so the story was changed.
This goes a long way to explaining why Kirby's last year on the book was a bit bland compared to the earlier work. Still a lot of great artwork, but the storytelling was much less ambitious. I'd guess that the behind-the-scenes stuff regarding this storyline was part of the reason he took the DC contract a year later.
Anyway, as published, Thor returns to New York to find it deserted, and finds Balder and the Warriors Three still reeling from their battle with the Thermal Man, who is then making short work of the US Army.
Thor briefly switches to Dr. Blake to help an injured soldier, and when they're in danger Karnilla rescues the other Asgardians dure to her love of Balder, earning Loki's scorn. Thor finally unleashes the full power of the storm to sweep the Thermal Man out to sea and up to the frozen north, where I guess he still is to this day.
While the story is a bit weak, the art is pretty powerful. This is Bill Everett's first issue of this run (he'd inked a single issue a few years earlier, and the Kirby Checklist has him with an uncredited assist to Klein in the previous issue), and it looks very nice for the most part. A few rough spots, but he'd quickly be up to speed and doing some great inking.
Kirby's original cover for this was rejected (see TJKC #14 / COLLECTED JKC #3 for it), and replaced with a Romita/Verpoorten job.