Many consumer-resource interactions require relatively close synchrony between their life cycles. If their life cycles depend on temperature, then climate change may affect the degree of synchrony. We developed a simple mathematical model for heat accumulation from which one can predict synchrony or mismatch based on a temperature time series. This work, with an application to Spruce Budworm and Balsam Fir is accepted at Ecography (with Sebastien Portalier and Jean-Noel Candeau).