Radiative and nonradiative decay rates of the $C{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{\phantom{\rule{0.16em}{0ex}}+}$ electronic state of ${\mathrm{N}}_{2}^{\phantom{\rule{0.16em}{0ex}}+}$ are calculated as a function of the temperature. This makes it possible to study the effect of the temperature on the photoemission spectrum and on the ion yields $I$(${\mathrm{N}}^{+}$) and $I$(${\mathrm{N}}_{2}^{\phantom{\rule{0.16em}{0ex}}+}$). It is shown that the temperature has different effects on the isotopes $^{28}\mathrm{N}_{2}^{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}+}$, $^{29}\mathrm{N}_{2}^{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}+}$, and $^{30}\mathrm{N}_{2}^{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}+}$. Our results confirm that, regardless of the temperature, predissociation is the dominant relaxation mechanism for vibrational states ${\ensuremath{\nu}}^{\ensuremath{'}}\ensuremath{\geqslant}3$ of the $^{28}\mathrm{N}_{2}^{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}+}$ and $^{29}\mathrm{N}_{2}^{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}+}$ molecules.