Domain morphology and temperature-dependent piezoelectricity in terms of piezoelectric coefficient d₃₃ and normalized strain d₃₃* of (K,Na,Li)(Nb,Ta,Sb)O₃ lead-free piezoceramics at the polymorphic phase boundary were investigated. Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) studies revealed a characteristic domain morphology comprising strip-like domains and featureless domains. Moreover, a facile method based on the field-dependent piezoelectric coefficient d₃₃(E) measurement was verified to characterize in situ temperature dependence of piezoelectric coefficient d₃₃, as an alternative for the conventional ex situ route. It was demonstrated that the normalized strain d₃₃* exhibits superior thermal resistance to piezoelectric coefficient d₃₃, though both parameters are susceptible to temperature variation.