September 1 was proclaimed as the World Day of Prayer for Creation by the Orthodox Church in 1989, and many other Christian churches have joined since then, with Pope Francis most recently in 2015. It was then extended to be a month-long Season of Creation, ending on October 4 (Feast of St. Francis).
Organize a prayer service
Could be something small or a city-wide ecumenical service. Anytime between Sept 1 and Oct 4.