Heatwaves are occurring more frequently in the US, and climate change is causing heat waves to become more intense, directly impacting human health, including heat-related illnesses and deaths, Xinhua news reported citing the CDC study published on Friday as saying. 

In the northwestern US, rising temperatures are projected to cause significant adverse health effects in the coming years, according to the CDC. 

Between June 25 to 30, most of Oregon and Washington were under a National Weather Service excessive heat warning. 

The record-breaking heat had the largest impact in the two states, especially the Portland metropolitan area, with temperatures reaching 46.7 degrees Celsius, which is 5.6 degrees hotter than the average daily maximum June temperature, according to the CDC. 

During May and June, a total of 3,504 heat-related illness emergency department visits were reported in the states of Alaska, Idaho, Oregon, and Washington. 

Approximately 79 per cent of these occurred between June 25 to 30, when most of Oregon and Washington were under an excessive heat warning. 

Males and people aged 75 and above were affected the most, according to the CDC. 

The northwestern heat wave had a sizable public health impact, said the CDC, adding health departments should develop response plans, and protect communities from heat-related illness and deaths.