Several times during the summer season, infrasound from rockets launched in the early morning at Cape Kennedy in Florida was recorded at Palisades, New York (1505 km to the NNE), beginning 85 min after launch. No other equivalent signals were recorded from summer rocket launchings later in the day, although strong signals are recorded from rockets launched at any time in winter. The strong winter effect is caused by the presence of strong stratospheric westerlies, which provide a good sound channel between the stations. This sound channel disappears in summer, when the stratospheric winds are easterly. The few good summer signals are explained by reflection above 100 km because tidal winds at that level in the early morning cause a favorable sound channel between source and receiver. The lower-frequency content of summer signals, compared with that of winter signals, is shown to result from attenuation of higher frequencies above 50 km.