The paper analyses a sample of daily coastal observations to reveal patterns of water temperature temporal variability in Martynova Bay for 2000–2020. In the time course of water temperature, a response (in the form of positive and negative extremes) to synoptic processes in the atmosphere and sea was tracked. In the cold season, three groups of such extrema were identified. These are clearly expressed maximums in November determined by the transfer of warm air mass from the Transcaucasia to the Black Sea; minimums in December–February due to Arctic invasions; and less significant highs in February–March caused by the foehn wind effect. In the warm half of the year, two groups of extremes were identified in the time course of water temperature. These are maxima caused by overheated air masses, which spread to the Black Sea from the Sal steppes in June–August, and minimums in June–September associated with the influence of the Black Sea upwelling. It is shown that in the bays of the northern coast of the Heraclean Peninsula, fluctuations in water temperature caused by surge winds were insignificant. Their range did not exceed 1 °C, and the duration of the cycle, as a rule, was no more than one day.