Mobile phone big data can offer new opportunities for identifying weather impacts on recreational ecosystem services in protected areas. This could be useful to assess how climate change could affect recreational ecosystem services. To explore these opportunities, we utilize mobile phone data and examine impacts of tropical weather (temperature, rainfall, and wind) and holidays on visitor numbers and stay time in an urban protected area in Singapore. These impacts were analyzed by visitors’ home regions and ethnic groups as well. The study results showed that rising temperatures below 31.7 °C had positive impacts on visitor numbers, in contrast to the common perception that cooler temperatures would be always preferred for outdoor activities in a tropical region. Meanwhile, these rising temperatures reduced visitor stay time in the protected area. Rain and wind had limited impacts on visitors. Compared to the weather variables, holidays had bigger impacts on visitors, particularly the Chinese group and those visitors living not close to the protected area. The study results highlight several advantages of mobile phone data application to analyzing weather impacts on public use of urban protected areas.