The answer is YES! Yes you can knit and crochet in summer. You just have to choose your projects with a little more thought and care. This is not to say that knitters and crocheters don't do this already, but in summer weather a little extra is required for your comfort.
Summer is the time for working with cottons, linen, bamboo and rafia and tarn. Tarn is yarn made from t-shirts cut into 1/2 inch to 1 1/2 inch strips. The t's can be old that have stretched or faded, new ones or the fabric before the shirts are cut out and assembled. Cottons can be the dishcloth cottons that are worsted weight down to the fine crochet threads. Linen, bamboo and rafia are all plant fibers that have many different characteristics, most of which I won't go into. Rafia can also be made from synthetics and have a sheen that borders on shine.
Summer is the time for small projects. In the heat of July and August might not be the time to work on a large wool afghan that was started in the end of winter but didn't get done. You could however, think ahead and if you prefer wool to plant fibers, work on small items like hats and mittens. Mostly though, when I think of summer work, I want to do things like embellish flip flops and baseball hats, dish cloths, small purses, or beach cover ups. I also think to do quick slippers and baby hats for donations. I like quick to finish projects because so much of my time early to mid summer is spent outside.
Here are a few ideas along these lines.
I offer these ideas and can teach these during basic beginner classes. Nothing shown here can't be done after a class or two. Basic stitches, cotton yarn and flip flops are all that are required.
I also think of afghan squares or granny squares. These are quick to make, not too hot to hold and easy for a brain that has been fried in the summer sun. I do them with an eye towards the coming winter and those who are not as fortunate. These blocks also give me a chance to practice techniques I want to learn or re-familiarize myself with.
Have a great summer! Posts will still continue. I'm also going to do a Christmas in July series of posts. Keep checking back.