There are several annuals which can be started from seed this month for early flowers next year. But.....what about late frosts and coldness of the ground?
Are they worth it? Or is it better to delay until Spring?
I sow my Hardy annuals in the autumn and overwintered in a cold frame. They had a good root system by the time I planted out in spring and got off to a flying start. Some people prefer to direct sow and plants can always be protected by fleece or a cloche if frosts are predicted. Just keep an eye on the weather forecast daily. If plants are lost you can always sow more in the spring.
What about slugs and snails? And weeds? They get more time to do their thing!
I find that if you have something that is happy to self seed, they get away with it just because of the volume of seed. That's fine if you want to grow the same thing every year. When I had an annuals patch the echiums and eschscholtzias came up reliably each spring, other people have nigella and opium poppies do the same.
If you are paying for something new it is probably safest to wait for optimum conditions, plant in clean soil and watch out for the molluscs. You might miss out on a few early flowers, but you will probably get more of what you plant. Then if you like them where they are you can let them seed themselves in autumn at no extra cost!