Drawing on transit smart card data coupled with weather station records across a 12-month period, this paper investigates the influence of local weather on urban transit ridership in Brisbane, Australia. A set of negative binomial regression models is applied at both daily and half-hourly levels to approximate the weather–transit ridership relationship across different passenger types. In addition, combining genetic algorithm and partial correlation, a new analytic approach is developed to capture the critical points in the weather–transit ridership relationship. The modelling results reveal that the influence of weather condition on transit ridership is not consistent in terms of passenger type and transit mode, and such characterised influence also has an obvious character of spatiotemporal heterogeneity. At the daily level, senior is found to be more sensitive to variations in weather condition compared to other types of passengers. At the half-hourly level, weather is shown a stronger influence on transit ridership during midday off-peak hours vis-à-vis either morning peak or evening peak. Furthermore, grounded in the new analytic approach, our modelling results also highlight that there exist critical points when weather variable reaches transit ridership varies substantially and those critical points are differed by transit mode, trip origin and time period. We argue our findings would be important in enriching an evidence base with the capacity to inform transit operators to (re)schedule and (re)design their transit services in response to all weather conditions.