Parramatta, nestled along the Parramatta River, boasts a humid subtropical climate, characterized by mild winters and warm to hot summers, accompanied by moderate rainfall throughout the year. This classification, under the Köppen climate system as Cfa, captures the essence of Parramatta's weather patterns, which are influenced by its geographical location and proximity to the Tasman Sea.

During the summer months, Parramatta experiences variable maximum temperatures, often exceeding 35°C (95°F), with an average of 13.1 days of such temperatures per summer season. However, temperatures can also remain in the low 20s, especially following the passage of cold fronts or sea breezes like the southerly buster. Additionally, hot winds from the desert, brought by northwesterly winds, can elevate temperatures above 40°C (104°F), particularly from November to February, with occasional spikes above 44°C (111°F) during severe heatwaves, as seen in January 2018 when the temperature soared to a record 47.3°C (117.1°F).

Notably, Parramatta tends to be warmer than Sydney CBD in summer due to the urban heat island effect and its inland positioning. This difference can be significant, ranging from 5–10°C (9–18°F), especially when sea breezes fail to penetrate inland on hot summer and spring days.

In terms of precipitation, the first three months of the year typically see slightly higher rainfall due to moist easterlies from the Tasman Sea, brought about by the position of the subtropical high to the south of the country. Conversely, the latter part of the year tends to be drier, particularly in late winter and spring, as the subtropical high shifts northward, allowing dry westerlies from the interior to prevail. Parramatta's location on the leeward side of the Great Dividing Range further contributes to drier winters by blocking westerly cold fronts and facilitating foehn winds, resulting in sunny days and lower precipitation.

Thunderstorms are common from early spring to early autumn, with occasional severe occurrences. Snow, however, is a rarity, having been recorded only twice in Parramatta's history, in 1836 and 1896. Despite this, Parramatta enjoys approximately 106.6 days of clear skies annually, offering ample opportunities for outdoor activities and exploration.

With its unique climate influenced by both coastal and inland factors, Parramatta provides residents and visitors alike with a diverse and dynamic environment to experience and enjoy throughout the year.