If you plant grasses, plant them in an open spot where the morning sun will light them up. Evening sun is good too, but this 'Karl Foerster' feather reed grass greets the early morning.
If you plant nasturtiums, plant bright orange ones. 'Whirlybird' is good.
You can plant them beneath a soft billowy bush clover -- this one is a dwarf Lespedeza called 'Ido Shibori' and it won't overtake the area -- but make sure the orange nasturtiums face east to catch the morning sun.
If you put ornaments in your garden, like a wooden obelisk, make sure to put them where the sun can find them first thing every morning.
That's all. That's your garden advice for a cool September morning.
Put stuff where the sun sees it first on its way up in the morning.