During El Niño years, the ocean currents change, which causes the sea surface temperature to rise in the eastern Pacific Ocean. As a result, the air above the ocean also heats up, and this warm, moist air rises and travels eastward. This can cause a shift in the location of the storm track, which affects the temperature and precipitation patterns in various regions around the world. In the case of Christchurch, New Zealand, the shift in the storm track can lead to more frequent and stronger southerly winds, which bring cooler air from the Southern Ocean and result in lower temperatures than usual.