There are two things that you should definitely try during the summer, when temperatures are high and you don’t really feel like cooking: baking cookies in your car and making homemade raisins. The former requires an 100F-or hotter day to work well. The latter simply requires a very warm sunny day, fresh grapes and patience.
Homemade raisins are easy to make and the finished product is well worth the effort. Raisins are formed when most of the water contained in a grape evaporates, leaving behind a slightly shriveled fruit that has a very high sugar content. They can take up to several days to dry out and go from “juicy grape” to “plump raisin,” and as long as you check on them once in a while, it is virtually impossible to over-dry them. Homemade grapes will almost always be more flavorful and sweeter than commercially produced raisins (although I’ve had some good ones at the farmers market before) because they’re fresher and still have enough of their natural moisture to keep them tender.
To make raisins, start with a bunch of fresh grapes. Rinse them well, and put them in a single layer on a flat surface. I use paper towel-lined baking racks, partially for cleanliness and primarily to increase the circulation of air to the fruit. Then, place the grapes out in full sunlight on a hot day and wait for the sun to do its work. I like to put a fine screen on top of the grapes to deter flies from approaching as they dry. The process will take about 4-6 days, depending on the weather and the sun exposure. Feel free to take the raisins inside at night, then put them out again in the morning.