Coimbra has a warm-summer Mediterranean climate in a transition to a hot-summer (Csa) version of the interior of Central Portugal. In winter, temperatures range between 15–16 °C (59–61 °F) at day and 5–7 °C (41–45 °F) at night and can drop below 0 °C (32 °F) occasionally (around 10 days a year), while summer temperatures range between 28–29 °C (82–84 °F) at day and 15–16 °C (59–61 °F) at night and can reach 40 °C (104 °F) or more in hotter days. Coimbra has around 32 days a year with maximum temperatures above 30 °C (86 °F). The lowest and highest temperatures ever recorded in Coimbra were −4.9 °C (23.2 °F) in 27 January 1976 and 42.3 °C (108.1 °F).
Precipitation is abundant throughout the year except for July and August.
Despite being relatively distant from the coast, Coimbra also has a marked Atlantic influence due to the floodplain of the Mondego River which crosses the city, making both its winters and summers milder than they would otherwise be. This influence also makes cold waves less frequent and less intense, however, days with minimum negative temperatures and cold waves are still present occasionally. Topography is also an important factor to consider in regard to nighttime temperatures, the presence of cold air lakes, in topographically depressed areas at certain synoptic situations, can also lead to pronounced colder temperatures.