One of the interesting aspects of html emails is how specifically they can addresses the current status of things. Few sites change or redesign based on the time of year; sure there are some subtle changes, but few sites make radical changes. Emails on the other hand are temporary and offer the opportunity to focus and being very sensitive to the context they are being sent in.
This collection of emails focuses on the summer season. All are pitching products in such a way as to appeal to consumers. It isn't really suprising that companies are doing this, but I do find it a bit suprising that there is such a common message across all these brands.