In the latest excellent Angel for Shabbat, Rabbi Marc Angel discusses the brit mei Noach, the covenant with humanity to not again destroy the earth, promised to Noah after the flood. The sign of the covenant is the rainbow, and for this reason the Talmudic Rabbis viewed the rainbow as a tangible sign of Hashem's presence (Hagigah 16a) and mandated a blessing upon seeing it. Rabbi Angel also points out that Rava said that one who sees a rainbow should do a full prostration to it, a beautiful and poignant suggestion especially in these times. Does anyone know the source of this comment? I don't think it occurs in Hagigah 16a, although I haven't checked it.
Also, here is a link to the beautiful prayer for creation put together by the good folks at Neohasid: