Green infrastructures (GI) are increasingly recognized as sustainable solutions for managing stormwater in cities. However, their capacity to maintain hydraulic connectivity with groundwater systems under winter conditions remains poorly understood. In Southern Quebec Province, winters are increasingly characterized by mid-winter thaws and rain-on-snow events, resulting in the infiltration of liquid water into GI when the soil is generally considered impermeable due to surface freezing. Whether this liquid water effectively infiltrates and reach the underlying aquifer remains uncertain. To address this, we conducted a two-year hydrological, geochemical and geophysical monitoring at three instrumented GI sites (in Montreal and Laval), using multi-piezometer networks equipped with pressure, electrical conductivity, and temperature sensors, complemented by sampling for stable water isotopes, major ions, and alkalinity. At one site, borehole-based time-lapse Electrical Resistivity Tomography (ERT) imaged subsurface resistivity, with elevated electrical conductivity from road salt serving as an infiltration tracer. Winter snowmelt triggers distinct groundwater responses, including rising water table levels, elevated chloride concentrations, and clear snowmelt isotopic signatures. Mid-winter thaw events are more challenging to detect, as groundwater electrical conductivity remains unchanged. However, apparent resistivity indicates transient infiltration of salted surface water, while post-event groundwater isotopic signatures confirm contributions from surface-derived water. These results highlight the importance of combining multiple approaches to better characterize groundwater recharge dynamics throughout the year.