NEW YORK - Weather was a hot topic at the US Open again on Tuesday, as players again battled high heat and humidity as well as each other in a bid for semi-final berths. A day after Roger Federer's hopes of a sixth title melted away in a shock loss to 55th-ranked John Millman, the US Open's extreme heat policy was again in effect, allowing a 10-minute break in both men's and women's matches that went beyond straight sets. "I had a shower, lay on the table and I didn't want to come back again," third-seeded Argentine Juan Martin del Potro said of how he spent the break in his 6-7 (5/7), 6-3, 7-6 (7/4), 6-2 victory over American John Isner.