Hot weather speeds the initial set, which can be problematic, but it can also be managed. Plenty of shotcrete pools get installed around here in the summer, where the daily highs are typically at least 35°C and often over 43°C. Water reducing retarder admix is generally used in the summer here, and whoever's responsible for keeping it moist during the initial cure has to be a lot more diligent about spraying it down in hotter weather. If it's being mixed on site or the batch plant is really close by, I wouldn't worry too much. If the batch plant isn't really close by, it could be problematic, even if they use a retarder admix.