In this work a simultaneous refractive index and temperature sensor is presented. The optical structure consists of a soda-lime planar waveguide coated with CuO thin film for the generation of two separated Lossy Mode Resonances (LMRs). One section of the CuO thin film is in contact with the external medium while the other part is coated with a thick layer of PDMS. As result of this, two different resonances are obtained, centered at 600 nm and 1000 nm respectively. The first resonance wavelength is modified by the external medium refractive index, while the second one is only affected by the PDMS refractive index, that due to the thermo-optic effect can be used to measure the ambient temperature. Using this simple structure, a dual sensor has been obtained, showing an RI sensitivity of 1600 nm/RIU and a temperature sensitivity of 1.12 nm/⁰C.