Data scarcity of traditional observations cannot reveal whether surface temperature capture the potential for urban heat stress. This study improves the dataset with 40,000 citizen weather stations.
When temperatures exceed 36°C and relative humidity passes 58%, citizens in China may experience heat stroke.
Humidity increases with warming. Theory and observations about how increased humidity translates into more extreme rainfall can be reconciled if attention is paid to data and methods.
The choice of a fixed relative humidity leads to a simpler picture of climate feedbacks than fixing absolute humidity.