SEASONS: Rome has a four-season year. Spring (March and April) weather is changeable--wet and gloomy spells alternating with bright and sunny spells. The Italians, who don't like this unpredictability, call it tempo matto ("crazy weather"). Summer (May through September) is hot and dry. Autumn (October and November) is the season of heavy rains and mild temperatures. Winter (December through February) is the season of moderate rains and cool temperatures. The better days of this period are considered "bracing".
SUNNIEST MONTHS: July and August are exceptionally sunny, with bright sunshine on some 88% of the daylight hours. Rome is a sunny city, however, and for the year as a whole, some 62% of the daylight hours will be sunny. This will range from a high of 89% in August, to a "low" of 47% in December.
During the summer, the cumulus clouds tend to increase and grow during the afternoons, making the mornings the sunniest time of day. During the winter, the early morning mists make the afternoons sunnier.
WARMEST MONTHS: Late June through early September is the hot season. During these months, however, the low afternoon humidities make the sensible temperatures (the ones you actually feel) about a degree or two cooler than the table temperatures. The hottest actual temperature of the year will be around 95░ (it will only feel like 92░), and will probably occur in July or August.
From late May through early October, most nights will be hot enough that you will sleep better with some sort of room-cooling.
COOLEST MONTHS: December through February. At this time of year, you can expect frosty mornings on one or two days a week. These below-freezing temperatures don't last, though; and you can expect the afternoons to warm up appreciably. Winter afternoons range from chilly to mild, with cool being the norm. Winter nights are chilly and damp. The coldest temperature of the year will be around 27░, and will probably occur in January.
Some amount of snow will fall in two winters out of three, but it rarely stays on the ground for long--especially in the city.
DRIEST MONTHS: July and August. Some 72% (five days out of seven) of the year's days will get no measurable precipitation; that is, they will get less than a hundredth of an inch. July will have about twenty-nine such days, whereas October will get only twenty. A "dry day" in the table, however, is one with less than a tenth of an inch--a more useful measure. It takes at least that much to wet the ground under the trees.
THINGS TO KNOW: In summer, the late afternoons are made more bearable by the westerly ponentino which usually blows in from the Tyrrhenian Sea about that time, dropping temperatures and bringing a delightful freshness to the otherwise hot summer air.
Romans consider early October (before the heavy rains start) as the most romantic time of year. Picnics and country excursions are popular, a continuation of the ancient celebration of "ottobrate". Once the heavy rains start, these outdoor excursions cease completely, and Rome concentrates on its "city life".