New York: Annual Weather Averages July is the hottest month in New York with an average temperature of 76 °F (25 °C) and the coldest is January at 35 °F (2 °C) with the most daily sunshine hours at 11 in July. The wettest month is May with an average of 114mm of rain. The best month to swim in the sea is in August when the average sea temperature is 73 °F (23 °C).