Forecasting heightened magmatic activity is key to assessing and mitigating global volcanic hazards, including eruptions from lateral rift zones at basaltic volcanoes. At Kı-lauea volcano, Hawai’i (United States), planar dikes intrude its east rift zone (ERZ) and repeatedly affect the same segments. Here we show that Kı-lauea’s upper and middle ERZ dikes in the last four decades intruded at regular intervals of ∼8 or ∼14 yr. Segments with shorter recurrence intervals are adjacent to faster-moving parts of the flank, and ∼1–5 MPa of tension accumulates from flank spreading in the time between dike events. Intrusion frequency was neither advanced nor delayed during magma supply variations, supporting the role of long-term flank motion on the timing of dike intrusions. Although fewer historical dikes have occurred near the 2018 CE eruption site in the lower ERZ and the adjacent slowly sliding lower eastern flank, similar tension accumulated between the 1955 and 2018 eruptions. Regular dike intrusion recurrence intervals indicate the importance of including both extrusive and (commonly neglected) intrusive activity in eruption hazard analyses.