Online search systems of four major newspapers in Japan were used to find long-term changes in the coverage of key words related to climate change and summer heat for the period 1990 to 2019. It is shown that the coverage of "global warming" has an interannual variation with maxima corresponding to the publication of IPCC reports, with a distinct surge from 2007 to 2010. On the other hand, the coverage of "heat island" decreased markedly and that of "heat stroke" increased rapidly in the 2010s.