The noncontact measurement of water uptake in microscale (1-100 mu m), thermoresponsive poly(N isopropylacrylamide) thin films is challenging We assessed the efficacy of three different 3 hydroxyflavone (3 HF) based fluorophores to monitor water uptake in pNIPAM thin films close to the lower critical solution temperature (LCST) at 25 and 37 degrees C These 3 HF fluorophores undergo excited state intramolecular proton transfer, yielding emission from normal (N*) and tautomeric (T*) excited state forms The emission intensity ratio log(I-N*/I-T*) and N* band position are environmentally sensitive Water adsorption in pNIPAM thin films follows a nonlinear, two phase process at low relative humidity, the adsorbed water disrupts polymer fluorophore hydrogen bonding, yielding small changes in log(I-N*/I-T) ratios and overall intensity, at higher relative humidity these intensity parameters (but not fluorescence lifetime) change dramatically, indicating a larger change in local polarity These probes are thus sensitive indicators of water uptake in pNIPAM