Another Marine Heatwave Induced Excessive Hot Weather Regime: East China/Japan

Climate Impact Company Daily Feature

Issued: Saturday, July 5, 2025

Highlight: Another marine heatwave-induced super heatwave, this time China/Japan.

Fig. 1-4: The June 25-July 3, 2025 temperature and precipitation anomalies for East Asia, the marine heatwave to the east, and 15-day temperature anomaly forecast.

Discussion: Yet another location struck by marine heatwave enhanced air temperature during late JUN/early JUL as East China (and Japan) have turned excessive excessively hot (and dry). During the 7-day period ending July 3, 2025, temperature anomalies range from 2-4C >normal for East China and South Japan and near 8C >normal in parts of Northeast China (Fig. 1). East China and much of Japan have turned much drier during the past week (Fig. 2). Helping to enhance the sudden anomalous heat and dryness is the presence of what has become a semi-permanent marine heatwave off the East Asia Coast extending past the Dateline (Fig. 3). Surface water in this location is averaging 2-6C higher than 1 year ago. The vigorous anomalous warm water is (also) helping to warm the middle troposphere increasing subtropical high-pressure strength leading to higher potential temperature across parts of the East Asia land mass. As stated previously, and most recently regarding the Europe heatwave, the MHW phenomenon is likely to intensify mid-to-late summer and maintain the hot and sometimes dry climate risk to nearby land masses. The latest 15-day temperature anomalies forecast by ECM indicates the recent hot pattern strengthens with 3-8C >normal temperature departures (Fig. 4).