  We studied the temperature dependence of the light yield of the linear alkyl
benzene (LAB)-based and mesitylene-based liquid scintillators. The light yield
increases by 23% for both liquid scintillators when the temperature is lowered
from $26\;^{\circ}$C to $-40\;^{\circ }$C, correcting for the temperature
response of the photomultiplier tube. The measurements help to understand the
energy response of the liquid scintillator detectors. Especially, the next
generation reactor neutrino experiments for neutrino mass hierarchy, such as
the Jiangmen Underground Neutrino Observatory (JUNO), require very high energy
resolution. As no apparent degradation on the liquid scintillator transparency
was observed, lowering the operation temperature of the detector to
$\sim4\;^\circ$C will increase the photoelectron yield of the detector by 13%,
combining the light yield increase of the liquid scintillator and the quantum
efficiency increase of the photomultiplier tubes.
