That may not mean much to anyone from outside the region.
Dreary gray and wet weather during early June is so common that it's affectionately (?) referred to as the Rose Festival Low. Thick gray clouds scud low overhead, pushed into Portland by the inevitable low pressure weather front. One can almost plan on real summer weather beginning the Sunday after the parade.
Folks are more familiar with the Pasadena Tournament of Roses Parade, but Portland's Grand Floral Parade is also "all natural." Floats are covered with whole flowers, flower petals, bark, leaves, seeds, and other plant products. The ingenuity of the designers is amazing when it comes to producing the desired effects. And the floats are more spectacular every year. After the parade the floats are usually parked at a public location so people can get a close-up look at them.
In addition, all equestrian units and motorized vehicles must sport floral arrangements.
Speaking of which, horses abound in the parade. Most regional rodeos are represented by their courts. Occasionally breed associations are represented. Paso horses strut their stuff, Friesians add Baroque sophistication, and Arabians provide a gust of desert air. The Budweiser Clydesdales and Wells Fargo stagecoach usually participate.
And it's not Portland without the One More Time Around Again Marching Band playing it's signature Louie Louie. With the sunshine glinting off the brass instruments!