This is a conditional request.
A simple (type 1) conditional such "If it doesn't rain, I will water the flowerpots" express a possible condition (not raining) and its probable result (I water the flowerpot).
Your sentence has a request instead of a result. The condition (not raining in 7 days) is possible; it may happen but I'm not sure. After 7 days and there hasn't been any rain then I ask you to water the flowerpot. If it does rain then I don't ask you for anything.
The situation would normally when you expect not to see the person. For example "I'm going on holiday for two weeks. If it doesn't rain in the next seven days...". I am asking now, so not "will ask".
This is very common pattern:
If you like fish, please try my sushi.
If the car is working, can you pick me up?
If your son passes his exam, please ask him to apply for a job.
In all cases the condition is possible.