We have investigated the response of the flux-locked output of several high-TcSQUID magnetometers to small changes in temperature and for magnetic fields 0–30 &mgr;T. The temperature responseDT≡d&Fgr;S/dTis observed to be linear in the applied magnetic fieldBaand can be as large as500 m&Fgr;0/Kwhere&Fgr;Sis the flux through the SQUID loop and&Fgr;0is the flux quantum. Our measurements can be explained using a simple model that takes into account the geometry of a given device and is based on the idea thatDTis due to the temperature dependence of the superconducting penetration depth. Our results can be used to optimize device performance in applications where the noise of a device is dominated by ambient temperature fluctuations. ©1997 American Institute of Physics.