I know, I know. You are reading this thinking, "Come on dude, water temperature? Water temperature!?" I agree, it sounds like I have gone over the edge and crossed into crazy land; however, stick with me because the temperature of you water does make an impact on your pursuit of the perfect, albeit better cup of coffee.
Before we get started, an obligatory disclaimer. In this post we are talking about the temperature in which you brew coffee, not the temperature in which you consume your coffee. We don't want to enter the fray of the age-old debate of room temp vs. "I want my coffee to burn my mouth."
A Happy Medium
Let's cut right to the chase then, in the words of Goldilocks we are going to want that water "not too hot, not too cold." The colder your water is when it makes contact with the coffee grounds, the more flat, less-extraction you will receive from the coffee. In contrast, the hotter the water when it comes in contact with the coffee, the less flavor you will extract from the coffee (NCAUSA). It sort of looks something like this:
So, we want something right in the middle...around 205 degrees Fahrenheit for most coffee brews.
A Change in Temperature
Of course, around 205 F. is a good starting point, the best temperature to use will depend on the brew method being used, and the coffee you are working with. Darker roast tend to perform better with a cooler water temperature, try closer to 195 F. Whereas lighter roasted coffees tend to perform better at the higher end of the spectrum - try 200-205 F. In any case, you most likely want to stay in that 195-205 F. range and flux up or down depending on what roast you are working with. We wont get into the complexities of brew methods and the impact of water temperature. The aforementioned is enough to get started with.
Tricks for Knowing the Right Temperature
Although I highly recommend an electric kettle that allows you to set the specific temperature (and hold it), not everyone can afford, or wants to go this level. For those individuals, here is a trick: water boils at 212 F., just above where we want our temperature the majority of the time. So, bring your water to a boil, and wait about 60 seconds for the water to cool to around 205 for Light Roasted coffee brewing. Wait around 2 minutes if working with a darker roasted coffee.