Fluid allocation in a well can be determined with a distributed temperature sensing system using data from a distributed acoustic sensing system. Flow data indicating a flow rate of a fluid through a perforation in a well based on an acoustic signal generated during a hydraulic fracturing operation in the well can be received. Warm-back data indicating an increase in temperature at the perforation can be received. A fluid allocation model can be generated based on the flow data and the warm-back data. The fluid allocation model can represent positions of the fluid in fractures formed in a subterranean formation of the well.