Nocturnal temperature variations around March-April 1999 at El Leoncito. Data are from February 22 (lowest curves) to May 2 (upper curve). This example shows the change of the semidiurnal tide from low-amplitude summer to high-intensity winter conditions. Maximum tidal amplitudes are observed in April. This is a regular feature that repeats each year and is also strongly present in the monthly mean tide. See preliminary version of monthly mean tide