May in Allentown averages a daily high of 22.5°C with nights around 9.9°C. Expect roughly 12.4 wet days totalling 93.6mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Allentown is May–June.
Based on ALLENTOWN LEHIGH VALLEY INTERNATIONAL AIRPORT, PA US (5.8km), 1995–2024. 30 years of May data.