  Ultracold atomic gases are an important testing ground for understanding
few-body physics. In particular, these systems enable a detailed study of the
Efimov effect. We use ultracold $^{39}\mathrm{K}$ to investigate the
temperature dependence of an Efimov resonance. The shape and position of the
observed resonance are analyzed by employing an empirical fit, and universal
finite-temperature zero-range theory. Both procedures suggest that the
resonance position shifts towards lower absolute scattering lengths when
approaching the zero-temperature limit. We extrapolate this shift to obtain an
estimate of the three-body parameter at zero temperature. A surprising finding
of our study is that the resonance becomes less prominent at lower
temperatures, which currently lacks a theoretical description and implies
physical effects beyond available models. Finally, we present measurements
performed near the Feshbach resonance center and discuss the prospects for
observing the second Efimov resonance in $^{39}\mathrm{K}$.
