Though this has developed into a very interesting discussion of wines we really have moved away from the original post which was referring to "Summer red wine recommendation" and specifically lighter styled wines.
I agree with someone who mentioned Rose as an excellent summer wine, to be consumed cool or chilled naturally. We have had some excellent Rose from Provence, and, of course, Mateus Rose is always excellent.
But to get back to reds I quite like a cool (not chilled) slightly sparkling red wine. The two that I prefer are Lambrusco, mainly from the region near Modena (
https://en.wikipedia.org/wiki/Lambrusco) or the much less known Bonarda dell’Oltrepò Pavese (
Wikipedia (Italian) - the Wikipedia entry does not really do it justice and the English version refers mainly to a different wine from Argentina). A quite pleasant Lambrusco can be had that has an alcohol content of about 11% but the similar styled Bonarda is a little more robust and usually has about 13% alcohol.