For any other people looking at this post, in my experience, you can get long term rentals outside of the peak summer season. If you contact apartment owners around October time, you often can rent the property at a cheap monthly rent right through until April.
In some circumstances, (where the owner has more than one apartment), you will be able to rent something over the summer months if you have already proven to be a reliable long term tenant.
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Hope that helps,
AZ