The radially outward propagating diurnal signal in the upper‐level clouds (diurnal pulse) is a prominent cyclical feature of tropical cyclones (TCs). This study examines relationships between diurnal pulses and TC intensity changes using satellite Infrared data from 2001 to 2018. The occurrence and duration of diurnal pulses 24 hr prior to or during TC intensity change are strongly correlated with TC intensification rate. Rapidly intensifying (RI) TCs have a markedly higher frequency (60%–80%) of very long‐duration pulse (≥15 hr) and significantly longer mean pulse duration than steady‐state (40%–50%) and gradually intensifying TCs (50%–60%). Long‐duration pulses are infrequent in weakening TCs (20%–30%). Diurnal pulse frequency and duration are highly correlated with the initial cloud‐top cooling rate and very cold‐cloud fraction in the inner core, but less related to the initial TC intensity. In short, strong diurnal pulsing of cold clouds is an evident signature prior to or during the RI of TCs. Plain Language Summary Clouds and precipitation in tropical cyclones (TCs) sometimes have an evident diurnal cycle, just like the regular daily weather systems. One dramatic feature is that cloud tops of the TCs oscillate like a wave propagating from the storm center out to several hundred kilometres over the course of the day, so called diurnal wave. This study uses infrared measurements from global satellites to study the relationships between the diurnal wave of cloud tops and the change of the TC's intensity. Results show that there are close relationships between diurnal waves and the intensification of TCs. Diurnal waves are more likely to occur in intensifying TCs than steady‐state or weakening TCs. The occurrence frequency and duration of the diurnal waves increase linearly with the intensification rate of TCs, for instance, rapidly intensifying TCs have significantly stronger and longer‐lived diurnal waves than slowly intensifying TCs. The frequency and duration of diurnal waves usually increase 24 hr prior to or during the TC's intensification, while they are relatively invariant after TC intensifying. In short, the diurnal wave of cloud tops is a potential predictor or indicator for the evolution of the TC's intensity and provides a new perspective for the study of TC intensity change. Key Points Tropical cyclones (TCs) intensification rate is strongly correlated with the frequency and duration of the diurnal pulse of upper‐level clouds in TCs Very long‐duration diurnal pulses are markedly more frequent in rapidly intensifying TCs than steady‐state or gradually intensifying TCs Occurrence and duration of the diurnal pulse is the best correlated with the initial inner‐core cloud‐top cooling rate