Avoid anything with PUL. Fleece covers are awesome in our weather. My stash consists on baby beehinds bamboo fitted with fleece covers, baby beehinds magicals (much prefer the minky ones) and itti bittis. As a small baby, I've always had them in baby beehinds bamboo fitted over summer. Also, during summer nappy free time is fantastic for bubs (and less washing for us mums lol).
Hope that helps.