Don’t stop crocheting because the weather is getting warm! Here’s a cool little cotton halter!
This was written with my six year old in mind, but both the neck and button waist strap are adjustable, allowing the shirt to grow with her. I expect she will be able to wear it for several summers, and it would also work for a slightly smaller child!

Any cotton DK yarn would work for this. Knit Picks Cotlin was what I had on hand. It could also be made larger by using a worsted weight yarn and a larger hook.