The temperature dependence of the electron nuclear double resonance (ENDOR) spectra of FH(CN−) centres in KCl was investigated in the temperature range between 10–220 K. At the lowest temperature of 10 K only one CN−orientation with respect to the F centre electron is present, in which the nitrogen is thought to be nearer to the F-electron than the carbon. With the very small thermal activation energy of 2.9 meV the opposite orientation is occupied. The superhyperfine interactions of those first shell K nuclei nearest to CN−and of the13C interaction of the CN−molecule are strongly temperature dependent between 10 and 60 K, following an exponential law with a thermal activation energy of 4.2 meV. It is assumed that a soft local mode involving those two nearest K nuclei and the CN−is causing the strong temperature dependence. The shf interactions of14N nuclei have not been seen, probably because of the dynamical effects.