Whether the Weather Matters: A Time-Series Analysis of Rainfall and Mechanical Thrombectomy Utilization and Workflow Metrics

Background and purpose Whether weather affects the real-world utilization and workflow of mechanical thrombectomy (MT) remains uncertain. We evaluated the association between daily precipitation and MT utilization and explored differences in workflow metrics. Methods We conducted a single-center, retrospective time-series study at Nagoya City University Hospital in Nagoya, Japan, over nine years, linking daily meteorological data from the national weather service to consecutive MT procedures. The primary outcome was the difference in daily MT occurrence between rainy (≥5 mm precipitation) and non-rainy days. Secondary analyses assessed stroke etiology strata, the relationship between precipitation amount and MT occurrence, and differences in door-to-puncture (D2P) times overall and during out-of-hours periods. Results Across the study period, 134 MT procedures were performed. The proportion of days on which at least one MT was performed was significantly higher on rainy days compared to non-rainy days (5.7% vs. 3.6%; odds ratio 1.63, 95% CI 1.07-2.42; p = 0.02), with a stronger signal for embolic strokes. A positive dose-response pattern was observed between precipitation amount and MT occurrence. Median D2P was shorter on rainy than on non-rainy days (101 vs. 131 minutes; p = 0.047), with the largest difference during out-of-hours (99.5 vs. 142.0 minutes; p = 0.009). Patient outcomes did not differ significantly between rainy and non-rainy days. Conclusions Rainy weather was associated with higher MT utilization and shorter D2P, particularly outside regular hours. These findings frame weather as a pragmatic signal for thrombectomy service demand and workflow performance, with potential implications for demand forecasting, on-call staffing, and protocol readiness. Prospective, multicenter studies with formal time-series adjustments are warranted to confirm generalizability and clarify mechanisms.