The article presents a smart flexible porous bilayer for all-day dynamic passive cooling, combining a polydimethylsiloxane (PDMS) upper layer with a hydrogel lower layer. The PDMS layer, with high solar reflectivity (0.930) and emissivity (0.952), provides excellent radiative cooling and protects the hydrogel from solar exposure. The hydrogel layer demonstrates remarkable water evaporation and absorption, achieving dynamic evaporative cooling. The synergy of the two layers enhances overall cooling performance. The bilayer achieves peak cooling power values of 424.4 and 650.6 W m\(^{-2}\) and maximum subambient cooling temperatures of 10.4 and 3.7 °C during sunny and cloudy mid-days, respectively. It also shows 3.2 °C warmer temperature during cold nights compared to the PDMS alone, indicating self-adaptive cooling properties. The bilayer's effectiveness is further demonstrated under continuous cloudy conditions, making it a promising strategy for efficient all-day dynamic passive cooling.The article presents a smart flexible porous bilayer for all-day dynamic passive cooling, combining a polydimethylsiloxane (PDMS) upper layer with a hydrogel lower layer. The PDMS layer, with high solar reflectivity (0.930) and emissivity (0.952), provides excellent radiative cooling and protects the hydrogel from solar exposure. The hydrogel layer demonstrates remarkable water evaporation and absorption, achieving dynamic evaporative cooling. The synergy of the two layers enhances overall cooling performance. The bilayer achieves peak cooling power values of 424.4 and 650.6 W m\(^{-2}\) and maximum subambient cooling temperatures of 10.4 and 3.7 °C during sunny and cloudy mid-days, respectively. It also shows 3.2 °C warmer temperature during cold nights compared to the PDMS alone, indicating self-adaptive cooling properties. The bilayer's effectiveness is further demonstrated under continuous cloudy conditions, making it a promising strategy for efficient all-day dynamic passive cooling.