We present structures of mouse TRPV3 in temperature-dependent open, closed and intermediate states that suggest two-step activation of TRPV3 by heat. During the strongly temperature-dependent first step, sensitization, the channel pore remains closed while S6 helices undergo α-to-π transitions. During the weakly temperature-dependent second step, channel opening, tight association of the S1-S4 and pore domains is stabilized by changes in the carboxy-terminal and linker domains.