Rome weather: the 1991-2020 normals

Rome's warmest month is August, mean 77.7°F (25.4°C¹) at the Ciampino station, just above July at 77.2°F (25.1°C); January is the coldest at 45.5°F (7.5°C), and the year averages 60.4°F (15.8°C¹).

What these figures are, and what they are not

These are climate normals for the 30 years from 1991 to 2020, the standard set by the World Meteorological Organization, computed on the stations of the Italian Air Force meteorological service. Italy submitted 84 stations to that dataset.

A monthly value gets published only when at least 24 of the 30 years are valid. Otherwise it is coded as missing and no annual total exists for that variable. Keep that rule in mind: Rome runs straight into it two sections down.

Month by month at Ciampino, 423 feet (129 m)

Mean, mean daily maximum and mean daily minimum, in °F with °C in brackets:

The annual mean maximum is 69.8°F (21.0°C) and the annual mean minimum 51.6°F (10.9°C¹). ISPRA, working on a separate homogenized series for the same station and the same period, puts that annual minimum at 11.1°C¹ against the 10.9°C¹ of the WMO series: two independent datasets, one decimal apart.

Rain: 622.6 mm a year, and almost none in July

Rome's own Ciampino series has no annual rainfall total at all: 3 summer months, June, July and August, fall under the threshold of 24 valid years. The complete Rome series comes from Fiumicino instead, at 16 feet (5 m): 622.6 mm² a year, November the wettest month at 98.9 mm², July the driest at 12.3 mm².

Fiumicino month by month, in mm: 53.8, 57.9, 51.5, 46.7, 37.1, 18.7, 12.3², 23.3, 59.8, 90.0, 98.9², 72.6.

Fiumicino sits on the coast, Ciampino inland and a little higher, and in every month both publish, Ciampino comes out wetter: 112.8 mm² against 98.9² in November, 91.8² against 90.0 in October. So the true annual total over the city is higher than 622.6 mm², by an amount nobody has published.

The station is not the historic center

Ciampino stands at 423 feet (129¹ m) on the edge of the built-up area, and the WMO series is exactly what it says it is: an airport reading. The center of Rome runs hotter through the urban heat island, and these normals do not quantify that effect.

Practical translation: on an August afternoon the 88.9°F (31.6°C) mean maximum is the floor for what a stone piazza will give you, not the ceiling.

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