Ollezy (French pronunciation: [ɔlzi]) is a commune in the Aisne department in Hauts-de-France in northern France.

Historical population

Year	Pop.	±%
1962	169	—
1968	162	−4.1%
1975	161	−0.6%
1982	163	+1.2%
1990	151	−7.4%
1999	158	+4.6%
2008	156	−1.3%

In 2010, the climate of the commune was of the degraded oceanic climate type of the central and northern plains, according to a CNRS study based on a series of data covering the period 1971-20001. In 2020, Météo-France published a typology of the climates of metropolitan France in which the municipality is exposed to an oceanic climate and is in the northeast climatic region of the Paris basin, characterized by mediocre sunshine, average rainfall regularly distributed across the during the year and a cold winter (3°C)2.

For the period 1971-2000, the average annual temperature is 10.4°C, with an annual thermal range of 15°C. The average annual cumulative precipitation is 684 mm, with 10.7 days of precipitation in January and 8.6 days in July1. For the period 1991-2020, the average annual temperature observed at the nearest meteorological station, located in the commune of Fontaine-lès-Clercs, 10 km as the crow flies3, is 10.8 °C and the annual cumulative average precipitation is 683.4 mm4.5. For the future, the municipality's climate parameters estimated for 2050 according to different greenhouse gas emission scenarios can be consulted on a dedicated site published by Météo-France in November 2022.

• Communes of the Aisne department