Coriander is a fantastic spice to use in cooking or as a herb tea during the summer months. It has a fairly rare ability to increase digestive fire (stimulate digestive enzymes) without aggravating pitta dosha (the dosha that controls fire and water and is often responsible for summer related digestive complaints).
During the summer months, our hunger and appetite tend to decrease somewhat. One ayurvedic explanation for this is that the pitta that is normally in our digestive tract is drawn towards our periphery in order to liberate heat through sweat, as well as digest heat and light reaching the skin. This can result in a weakened digestive fire which can in turn cause heaviness and indigestion after meals.
The fresh leaf is also excellent for the same purpose, though somewhat less potent. It is however very cooling and useful to use as a tea if you have an acute case if inflammation, such as a urinary tract infection.
If UTIs are common for you in the summer, likelihood is that you are not drinking enough water, or, using too many sour, spicy, salty or overly refined foods, all of which aggravate pitta and add to the bodies already increased heat due to the season. Drinking several cups of coriander tea (or better still, equal parts coriander, cumin and fennel) will help counter this tendency.