Unusually hot and dry weather happening at the same time can put serious stress on forests. These events, called compound heatwave and droughts (CHWDs), can severely affect forest health, but their impacts are not well understood in the Pacific Northwest. This study looks at how CHWDs affect tree growth in a conifer forest in northern Idaho, and whether forest thinning (removing some trees for fire protection) helps or harms tree response. We studied four common tree species by examining their annual growth rings before and after thinning in 2019. We also used local weather data to understand how temperature and rainfall influenced tree growth during extreme events. We found that thinning made trees more responsive to climate—both positively and negatively. For example, thinning helped trees grow better when water was available, but also made them more vulnerable to extreme heat, especially western larch. Differences between species also became less noticeable after thinning, suggesting that all trees were more strongly affected by the same environmental conditions. This work helps us understand how forest management decisions might influence tree survival and will be used to improve computer models that predict forest responses to future extreme weathers.