The OSU Fall Gardening Guide should give you some ideas.

Fall Guide

So far all I have planted is fall tomato plants, but my spring peppers, watermelons and cantaloupes will produce until the weather cools off significantly.

I'd like to plant some leafy greens, but I doubt I'll sow a single seed until we get some sign that it will rain again. We have gone nearly 5 weeks without rain and it has been too hot to clean out the full beds in the garden to make room for fall veggies....and I wouldn't want to have to nurse seeds and seedlings through the hot, dry period we're currently experiencing. I am hoping rain comes soon, but we do not have a significant chance of rain in the 7-day forecast. They put a 20% chance of rain through 1 pm in our forecast for today, and it seems unlikely it will happen, but then there's no rain in the forecast for the rest of the week. My soil temperatures are really high too, and our mulch is pretty skimpy this year as the heavy rain in spring and early summer made it decompose much more quickly than usual.

I usually can get away with planting leafy greens in September, or even October for spinach, but it just depends on how much decent weather we get in between the time the rainfall returns (often in September, but occasionally later) and the really cold weather arrives.

Remember that planting late is risky because plants grow more slowly in autumn's increasingly shorter day-length and increasingly less intense sunlight. I only plant late when intensely dry weather forces me to.

In my best fall garden ever (might have been 2010 or maybe 2012), I ruthlessly tore out summer plants while they were still producing and planted the entire front garden with several varieties of kale, several varieties of cabbage, several varieties of beets, purple winter sprouting broccoli, several kinds of mustard greens, tatsoi, a mesclun lettuce mix, collards, spinach, radishes, carrots, Swiss chard and probably other things I've forgotten. Everything grew well and got big and was very healthy and we ate from that winter garden until it was time for me to take out the plants to make room for spring plants. It was a nice rainy fall and winter, but not excessively so. Sometimes frost damaged the plants, but it didn't kill them. They made most of their grown in autumn and early winter. After that, they mostly just sat there and grew slowly, if at all, but we were able to harvest and eat the plants slowly over a long period of time. Once daylength reached a certain point in spring, everything looked like it was starting to bolt, so I yanked out everything and put in new crops. Every year is not like that. Sometimes winter is too wet (and things rot off at the soil line) and sometimes it is too hot and dry and plant growth is poor. Since we are in an El Nino year, we ought to have a nice, rainy fall and winter so a fall garden ought to produce well. With our weather, though, you never know.

I did all the things mentioned above and so far things are just barely popping.

The seed embryos have a hard time in this heat. Now that the weather is cooling off some, maybe you'll start seeing some more seed germination and plant growth. Often the small plants seem like they just sit there and don't do much of anything until we get closer to the end of August and the temperatures become more moderate.