Hi Molly,
to ATP.
I started these on the soil surface. Tiny seeds usually need to be very close to the top to survive. You will need to keep them moist until they sprout. In your climate you may be able to scatter seed on an outdoor seedbed and get good results. Here, I must start indoors before frost leaves the ground, to have the plants ready to bloom before it gets too hot. They fritter away at that point.
I think if I lived where you do I'd start them as soon as it starts to cool off ... beginning or middle of your winter perhaps? Keep them moist for two weeks and they should pre-sprout. Once the timing is right for them they should begin to push up and grow. These plants do grow really fast, so that's a strong point in their favor. I think they know that they need to bloom and be pollinated before the heat to be able to reproduce.
If it's still dry, warm or windy when you sow you can cover the seeded area with Tulle fabric to help retain constantly damp soil. This also helps to moderate any rainfall; the fabric will lessen the impact of heavy water drops which might push your seeds too deeply into the soil.
Best of luck to you.
