Climate almanac

Oswego

Illinois, United States · 41.68°, -88.35°

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What is the climate like in Oswego?

The best time to visit Oswego is typically August – September, with trip comfort peaking in September (7.0/10). Oswego is warmest in July, when daily highs average 84°F (29°C), and coolest in January, when lows fall to about 20°F (-7°C). The wettest month is typically May and the driest is February; the year sees roughly 42 in (1074 mm) of precipitation.

  • Best time to visitAugust – September — comfort peaks in September (7.0/10)
  • Warmest monthJuly — average high 84°F (29°C)
  • Coolest monthJanuary — average low 20°F (-7°C)
  • Wettest monthMay (5.0 in (126 mm))
  • Driest monthFebruary (2.2 in (55 mm))
  • Annual precipitation42 in (1074 mm)
  • Based on2016-2025 daily ERA5 reanalysis data (10-year normals)
  • Records fromAurora Water, 11 km away (1893-2026)