The expected heat over the next three months will be partly caused by a shift in global atmospheric circulation patterns as the El Nino effect wanes, according to the JMA. The JMA also said that if the conditions for high temperatures converge, this summer will be as hot as or even hotter than last summer, which was the hottest on record. In preparation for another scorching summer, the JMA and the Environment Ministry launched Special Heat Stroke Alerts on 24 April. These come in addition to conventional Heat Stroke Alerts and will be issued when the Wet Bulb Globe Temperature (WBGT), an indicator to show the risk of heat stroke, reaches 35 degrees across a prefecture. While the WBGT has never reached 35 historically, Shotaro Tanaka, head of the JMA's abnormal weather information center, nevertheless urges caution.