It's HOT here in the Pacific Northwest. We've had temps hovering around 100 degrees for three days. That's intense - especially for June and for a region where a fair number of folks don't have air conditioning.
In these hot temps, I still drink hot tea. I choose teas that do best with cooler waters, often greens and especially Japanese greens, like sencha (ironically, in the photo above, I'm not drinking a Japanese green).
There are several ways to cool the water: Take it off the heat before it reaches a boil, let it sit off the boil before using, or - as shown above - use a cooling pitcher. The cooling pitcher (yuzamashi) is a common feature in sencha sets (also in Korean tea sets).
I'm not using a thermometer, so I'm guessing at the temperature. I sense that it's cooled to around 160 degrees. After pouring the cooled water into the pitcher, I generally pour off at about 30 seconds, adjusting on the second brewing, as appropriate (usually a wee bit longer).
I confess: I've brewed some senchas really poorly, and more times than I care to admit. It's always because I've been distracted. This is a tea that requires your full attention.
Below: I'm decanting straight into my teacup, but it's also possible to use the water cooling pitcher as a serving vessel. Note that the tea will continue to cool in the wide-mouthed vessel, so at this point (the tea is done brewing), you want to serve quickly.
You don't need anything fancy to cool the water. You can even use a Pyrex measuring cup.
Experiment and find the right process for making yourself a great cup of green tea with cooler water.