Ran a big basement slab in Tucson last Tuesday. Humidity jumped to 90% mid-pour. My power trowel kept grabbing, left those burn marks before the set. Switched to hand troweling the last 40 yards, came out smoother. But now I wonder if I just got lucky with the timing. Anyone else ditch the machine when the weather shifts fast?
Caught a podcast with a flatwork crew out of Phoenix that swears by hand tools whenever the dew point climbs past 60, said the machine just gets ahead of the moisture. Your burn marks sound like the classic float blading from a wet edge, that grab happens fast when the surface sheen dries quicker than the core. Timing matters more than the tool when humidity spikes, so I'd say you made the right call ditching it.