It's the exact reason that I always started everything I could in pots, then transplanted the starts to the ground. We have rain for about 8 or 9 months out of the year. Usually, it's fairly gentle rain, but in the spring, we have some real gully-washers, along with major thunder-boomers!
Between the slugs, snails, hungry animals, and the rain, it's a miracle if anything grows from a little seed. Only larger seeds, like nasturtiums and sweet peas, are likely to survive, and if we have a cold, wet spring, they'll just rot in the ground.