Timing is a big factor in manual weed control. Rain that comes on schedule keeps the weeds going even in this desert climate. If the rains come far apart, only a few weeds survive, no matter how much it rains. If it rains once a week or more, even if the rain is fairly light, the weed seedlings have a chance to progress until their roots go deep enough to survive dry spells.
Time plays another part. If it's wet and rainy when I have time to weed, I don't brave the weather for this chore. If I'm busy until the ground bakes hard, The weeds are hard to remove entirely, leaving sections of root behind to give their clones a start. If I water the soil (What a waste!) and return to pull weeds the next day, the ground has softened, but if I am distracted from this chore, it doesn't take long for the earth to bake hard again.
Going to seed is another time-related problem. In desert climates, many weeds go to seed quickly. They have evolved to survive in a place where rains may be brief, and they must produce seed before a lack of moisture kills or stunts them. It creates a lot more work if they have a chance to spread their seed.