Interaction between the lower thermosphere, at 40¿N, and the stratosphere has been found during stratospheric warming events. This interaction shows a temperature decrease of the lower thermosphere of about 10¿K (with a 95% confidence interval from 4.2¿K). Cooling already occurs by the time of peak stratospheric warming: however, maximum cooling appears nearly one lunation later. The measurements show the average magitude of the cooling effect to be independent of solar activity, magnetic activity, and other long-term secular variations to which the temperatures in the lower thermosphere are sensitive and to be independent of a 34¿ longitude separation in observing sites. The results indicate that the magnitude of the cooling effect may be dependent on the time of occurrence of the stratospheric warming during the winter: however, there are not enough measurements to test this contention fully.