Summer temperatures in Oxford peak around 25 C, with cooler temperatures at night near 12 C. Humidity can be high, and is usually over 50% throughout the day.
During the winter, expect highs of 10 C with lows just below 0. It does occasionally snow here, but only rarely and hardly ever in great amounts.
Rain falls throughout the year, so be prepared with an umbrella and raincoat whenever you come.
Summer is generally considered the tourist season and winter the off-season, although visitors come throughout the year and there is not a striking difference in hotel pricing or in the levels of crowds.