Why Cloudy Cities Are Good for Us

By Jeff Opperman, The Nature Conservancy

Most people love blue skies and clearly prefer being drenched with sunshine rather than rain. The sunny regions of the country are booming as people move to where they know the calendar will be filled with blue-sky days.

But think a bit more about what a blue sky means. In other words, think about the absence of clouds.

If you know where your water comes from, you know towns and cities draw their water from rivers, lakes or groundwater. These sources are replenished by rain and snow, and we all know that rain and snow come from… clouds.

So clouds are like water-delivery trucks rolling into town. What does this say about places with clear, blue—and cloud-free—skies?

To better understand the relationship between clouds and water supply, I did a very quick analysis of some readily available numbers.

  • First, I looked at SustainLane’s ranking of the sustainability of major U.S. cities’ water supply systems. These rankings provide an indication of how reliable or, on the other hand, how stressed or vulnerable a city’s source of water is.
  • Second, for each city I looked at the average number of cloudy days per year, from the National Weather Service.

The result shows that the most water-sustainable cities are the most cloudy, and the least water-sustainable cities are those with the most sun. (See the graph on the next page; the most water-sustainable cities have low numbers and are on the left side of the graph.) This correlation will not shock anyone who remembers the hydrological cycle from high school.

The 10 most water-sustainable cities have, on average, 160 cloudy days and 93 days of full sun. The 10 least water-sustainable cities are nearly the mirror image: 90 cloudy days and 168 sunny days per year. (For those who like statistics, let’s just say the differences in these averages are highly significant.).

While the bottom five cities for water sustainability (the very sunny Las Vegas, Phoenix, Mesa, Tucson, and L.A.) grew by an average of 37 percent from 1990 to 2000, according to Census data, the five most water-sustainable cities actually lost population, with an average loss of 3 percent.

In fact, of the five most water-sustainable (and cloudy) cities, only Chicago grew. The other four—Cleveland, Milwaukee, Detroit and New Orleans—all lost population.

There are two reasons for concern here.

First, rapidly growing populations threaten to outpace water supplies in many cities. Even in the relatively wet Southeastern United States, recent droughts have revealed that booming populations are straining water supplies in places like North Carolina and Atlanta.

These trends will be worsened by climate change, which is predicted to increase drought risk throughout the United States. And the regions most at-risk for climate-change-induced drought encompass the cities that today have both the lowest water sustainability and rapidly growing populations.

In short, Americans are collectively moving from the places that are best equipped to deal with climate change to those that are least equipped.

The second reason for concern is that supplying water to regions that lack abundant local supplies requires intense manipulation and alteration of rivers. Massive dams store water for diversion into long canals—artificial rivers for cities that lack their own. The result is blocked rivers, decimated populations of salmon and other native fish, and parched deltas and estuaries (where rivers meet the sea).

For example, dams on the Colorado River provide the water to support the rapid growth of cities from San Diego to Las Vegas to Phoenix. But as a result, the Colorado River rarely flows to the sea and its delta has now been reduced to 5 percent of its original size.

The Colorado Delta was once one of the world’s great desert estuaries. Legendary conservationist Aldo Leopold fell in love with the place, enraptured by its labyrinth of channels and ponds fringed by lush vegetation, teeming with birds and haunted by the nocturnal screams of jaguars.

I don’t mean to pick on any one city here. But I do want to raise awareness of the implications of our choices about where to live.

If you live in a place where it’s rarely cloudy (e.g., Las Vegas), or where it never rains during the warm half of the year (e.g., California), understand that getting water to your tap requires a massive reworking of natural systems and that water is particularly precious in such places.

And if you live where you wish you saw more of the sun, remember those clouds are water-delivery trucks lining up to keep your city sustainably watered and more resilient and prepared for climate change.

Jeff Opperman is The Nature Conservancy’s senior advisor for sustainable hydropower. He works to promote ecologically sustainable water management in river basins with hydropower infrastructure. Through this work, Jeff has provided strategic and scientific assistance to environmental flow assessments for several rivers in the United States and for the Yangtze River and the Patuca River (Honduras).

(Top image: A sunny day at the beach on Lake Erie. Though blessed with plentiful freshwater, such blue-sky days are less common in Northern Ohio than in much of the country. Image credit: Jeff Opperman. Lower image: on left, the parched Colorado River Delta in Mexico, showing the maze of twisting channels that once were filled with water and surrounded by lush forests and wetlands; on right, Phoenix, AZ, with lawns, golf courses and pools sustained by Colorado River water. Image credit: Google Earth).


Dave C.
David C3 years ago

..however, if too many cloudy rainy days people will move to the sunnier drier ones...... too many wet cloudy days this "spring and summer" in MN

Qian Zheng Yi
Jabi Yeonnmin4 years ago

Thank you

Heidi R.
Past Member 5 years ago

Good information - thank you.

I lived in a city where there were almost no clouds ever and I felt it affected my moods too, and not in a good way. We need clouds for many, many reasons it seems.

Laura M.
Past Member 5 years ago

Hmm, people living in dry cities should look up greywater systems. ^_^

heather g.
heather g5 years ago

Canada has an abundant supply of water, but people waste it - so there are water restrictions in summer. Where I live the infrastructure was cheaply built and the water usage is almost double that of any other areas as a result of all the wastage and leaking pipes. Many of the rivers have new power supply developments, so the natural flow is affected and the salmon runs are detrimentally affected. Water quality is not always up to par.

I was born in a sunny country and the main difference in people is that in sunny countries people have sunny personalities and seem to enjoy life a lot more. They also have greater respect for their resources, so do not waste water.

Susan A.
Susan A5 years ago

Interesting info...

Rachel R.
Rachel R5 years ago

but cities draw the rain to themselves, when you really want it to fall on the water catchment/agricultural land outside. Changing cities to CATCH and USE more of their own water, instead of just letting it go down the drain is a good idea!!

Sue L.
Sue L5 years ago

I understand the science behind the author's article and he makes some good points. But I also know that I prefer living in an area that gets much more sunshine than Northeast Ohio (Cleveland) does. And, fortunately water isn't an issue here in Minnesota-the land of 10,000 lakes.

Ruth P.
Ruth P5 years ago

I always think I don't like grey skies, but I miss them when I'm somewhere sunnier. I love the days here in England when the sky is a beautiful soft grey, and the sun shines through onto the green fields... it's wonderful.

Pat W.
Pat W5 years ago

I will stay where I am at.
I live in a varied seasonal area
I am lucky