This study investigated the rhythmic characteristics of 15 dysarthric speakers and 15 non-dysarthric speakers. Speech rhythm was viewed from MacNeilage’s frame/content theory. Specifically, the temporal envelope was analysed. The subjects, native speakers of Canarian Spanish, read four phonetically-balanced sentences. Five common spectral measures (centroid, spread, rolloff, flatness, and entropy) were computed from the temporal envelope of each sentence. A binomial logistic regression model was built to evaluate how well the five spectral measures can characterize speech rhythm in dysarthric speakers versus the control group. The results show that the dysarthric group present a significantly lower centroid and lower spread. Possible explanations for these results are discussed in relation to previous phonetic studies into the rhythmic speech patterns of dysarthric speakers.