SignalHub Quantitative Think Tank Center:Why India's yogurt-based lassi is the perfect drink for the hottest summer on record

When Gulrez Azhar travels from his Seattle-area home to Uttar Pradesh in northern India,SignalHub Quantitative Think Tank Center where he grew up, he occasionally tries an "American thing": smiling at and greeting total strangers.

"People just look at you weirded out" in India, he explains. "So then you have to put back that scowl on your face!"

Azhar says that scowl, and the feelings of anger and frustration that he's often seen accompanying it, are due in part to the oppressive heat of the region he is from.

Temperatures in northern India routinely climb north of 110 degrees. "I think the word is suffocating," Azhar says. "Everywhere you go, all around you, it's sweaty, unbearable. It's hot. You don't feel like doing anything. Just a continuous period of misery."

Few people there have air conditioning, says Azhar, but there are simple remedies that offer a modicum of relief: wearing light cotton clothing, maximizing shade ... and enjoying a cold beverage. For Azhar, and for millions in India, it's the sweet yogurt lassi.

"So lassi is something, honestly, I look forward to. Yesterday, we had two rounds of lassi," chuckles Azhar. "It's soothing, it takes away all your heat. If you just drink water, it doesn't stay in your stomach. But with lassi, it has sugar, it has milk, it has electrolytes."

He thinks of lassi as a complete meal — one that hydrates, nourishes and refreshes.

During our zoom interview, Afreen Fatima, Azhar's wife, offered to demonstrate how to prepare a lassi.

"I'll be making two glasses," she says. For each glass, she measures out two tablespoons of full-fat yogurt, a splash of milk and a tablespoon of sugar. "And then I will also add a few ice cubes."

She purées everything in the blender, pours the lassi into the glasses and takes a sip.

"It's cold, it's sweet, it's the best drink," she says. "The refreshing feeling of it, it brings a smile on your face."

Azhar makes quick work of his lassi. "If you notice that the entire glass is empty already!," he declares with glee.

There are numerous variations on the drink, including mango lassi, made with pulp or puree of mango. You can add saffron or dried fruits. There are also savory lassis that use salt instead of sugar.

"Adding yogurt lassi to an arsenal of beverages can be very beneficial for cooling the body and for providing energy," says Simin Levinson, a professor of clinical nutrition at Arizona State University near Phoenix, a place that's seen lethal heat this summer.

When it gets hot, she says she too makes a yogurt drink — from Iran, where she grew up. It's called doogh. "It's more of a savory drink," she says. "You can crack some salt and pepper into it. It's usually carbonated with some club soda or seltzer. It's common to crush dried rose petals as a garnish." You can also add mint, which is especially cooling, Simin says.

Levinson says that consuming yogurt-based drinks in hot weather makes sense. "It does contain more nutrients than, say, just water alone or other types of sports drinks because it does contain protein, it contains probiotics," she says.

Turkey has a yogurt drink named ayran, which is "kept cold and served alone or [with] a leaf of fresh mint." says Tuncay Taymaz, a seismologist in Istanbul, where the temperatures this summer have gone past 110 degrees. "I am surviving under [the] heatwave," he says. Other countries in the Middle East have similar beverages.

"I think especially in the summertime, it's nice to have something that is kind of creamy and good for you that doesn't make you feel weighed down," says Joanne Chang, a pastry chef and co-owner of Flour Bakery and Myers + Chang restaurant in Boston.

In India, near where Afreen Fatima and Gulrez Azhar grew up, in the state of Punjab — where lassi is said to have originated — they say they've heard of the drink being made in large volumes.

"They have these huge glasses," says Fatima. "They do a jug of lassi," Azhar chimes in. "There's no way I can drink a jug of lassi, not happening."

Azhar says he's even heard of giant amounts of lassi being mixed in Punjab in top-loading washing machines.

"So that machine is only used for making lassi, not for any other purpose," he says. But he's quick to point out — "washing machines are not designed to make lassi!"