*2.1. Materials*

The meteorological data used in this paper were obtained through the Meteorological Unified Service Interface Community of China Meteorological Administration. The decision tree method uses the regional average precipitation of 34 national meteorological observing stations in Chongqing (Figure 1), while random forest analyzes the precipitation of 34 national meteorological observing stations.

**Figure 1.** Map of 34 national meteorological stations in Chongqing.

The circulation index in this article comes from the business meteorological network [17–20], respectively, including atmospheric circulation index 88 such as the subtropical high, east Asian trough, polar vortex, Eurasian circulation type, characteristics, Pacific Ocean trade winds etc., SST index 26 such as ENSO (various districts and types), warm pools, Indian Ocean, Tide area, Kuroshio area et al., cold air and typhoon, Southern Oscillation Index (SOI), The Pacific Decadal Oscillation (PDO), Quasi-biennial Oscillation (QBO), subsurface SST index and another 16; in total, 130 items. Among them, the SST index in this article includes 26 SST indexes and 16 other indexes including multivariable ENSO index, decadal oscillation in the north Pacific, meridional mode SST in the Atlantic Ocean, quasi-biennial oscillation, EU300T\_130E, EU300T\_160E, EU300T\_180W, and Atlantic SST triples. In this article, summer refers to June to August.
