Babywearing in Summer
A one layer carry or sling maybe helpful - so a ringsling or a kanga-carry or front wrap cross carry with the passes gathered either side & if age & stage appropriate, a hip or back carry will also be a cooler way to use your sling.
Many of your favourite sling brands also offer "summer" or lighter weight versions of their carriers - e.g., Integra have the Solarweave version, Tula has the Tula Coast, Izmi has the Izmi Breeze, Beco have the Cool Mesh, etc... If you haven't already bought a sling, this might be something to consider, or you might like to find a local sling consultant or sling library & hire one instead!?
Some find it helpful to use a muslin square between you & baby - this can help to wick away excess moisture. Always be careful to ensure this is not going to compromise baby's airway.
Ultimately, if it's really hot, you may only want to babywear for short periods - but seek out the shade & take a break if you need too.
Happy, Sunny, Babywearing 😎