The southern Chinese tech hub of Shenzhen just recorded its wettest July in 31 years, with small businesses and airline passengers feeling the effects.Last month’s deluge was bad news for Yuan Zhang, who runs a small breakfast shop near a subway station in the city. Her monthly profit more than halved as weeks of persistent rain kept customers away.She spent 200,000 yuan (US$27,900) setting up the eatery, which opened last year, and made monthly profits of more than 10,000 yuan last...