It was hot this summer. Actually — it *is* hot this summer.
I’ve been traveling, first in Europe and more recently in Miami, and I’ve noticed more than ever the enormous difference in temperature between shaded and unshaded streets. During our time in Barcelona, I said it to my husband again and again: walking in the shade wasn’t just tolerable, it was genuinely pleasant. I could stroll for hours and barely break a sweat. But the moment I stepped across the street into direct sun, I’d be reminded just how brutally hot it actually was.
It reminded me of research I’d come across about the importance of tree canopies in cities — especially now, as heat waves arrive more often and climb higher every year. So I went back and dug into it. Honestly, the numbers blew my mind, so I wanted to share them here.
The best part: this is something we can act on *locally*. It’s worth a few minutes to read. Summers are only going to get warmer — but if we take action in our own neighborhoods today, our kids can have some real relief in the shade tomorrow.
Just how much cooler is the shade?
A lot cooler than you’d guess.
A 2024 study published in Communications Earth & Environment, led by researchers at the University of Cambridge, found that urban trees can lower pedestrian-level air temperature by up to 12°C (about 22°F)* through a combination of shade (blocking radiation) and transpiration (which is when the water vapor trees release, cools the surrounding air like a natural evaporative cooler). In the same study, introducing trees brought peak monthly temperatures below the 26°C “thermal comfort threshold” in 83% of the cities studied.
That 12°C figure is the ceiling under ideal conditions, but even the averages are impressive. A global analysis of 806 cities (highlighted by the World Resources Institute) found that increases in tree canopy are associated with midday “land surface temperature reductions of around 1.5°C (2.7°F)” — and that trees can make it feel up to 14°C cooler where you’re standing.
The effect scales with how large a tree canopy you have. Research summarized in Theoretical and Applied Climatology (2025) found that for every “10% increase in vegetation coverage”, land surface temperature drops by roughly 0.6–1.2°C. (I will mention that the benefit plateaus once coverage gets very high, around 50–60% in some cities — but most neighborhoods are nowhere near that point, so there’s enormous room to grow.)
And the cooling is dramatic where trees replace hard surfaces. A study of 293 European cities found that areas shaded by urban trees ran “ 0–4°C cooler in Southern Europe and a remarkable 8–12°C cooler in Central Europe” compared to built-up “urban fabric.” Notably, treeless green spaces (think open lawns) were “two to four times less effective” at cooling than actual tree canopy. Grass is nice; shade is what makes the biggest impact (makes sense!).
What Europe’s cities are learning
If you are still not convinced of the impact, there is even more compelling evidence from European cities, where researchers have connected canopy not just to temperature but to human lives.
A landmark 2023 study in The Lancet, led by the Barcelona Institute for Global Health (ISGlobal), they modeled 93 European cities and found something mindblowing: during the summer of 2015, cities ran about 1.5°C warmer than surrounding countryside, and roughly “4.3% of summer deaths were attributable to that added urban heat”. BUT: The hopeful part? The researchers estimated that raising tree cover to 30% (Europe’s cities average just under 15% today) would have prevented about “one-third of those heat-related deaths” — thats roughly 2,644 lives in that summer alone —
A newer 2026 study (npj Urban Sustainability, Nature) reinforced the pattern: across European capitals, a “20% increase in tree cover” reduced the probability of warming by 6–12%, with the strongest effects in Southern Europe — reaching up to “14% in cities like Athens, Lisbon, and Madrid”.
The lesson? Its pretty simple really: more canopy, cooler streets, and — where the heat is most dangerous — real reductions in illness and death.
Why this matters more for little bodies
Here’s what people dont talk about in the media: children don’t experience heat the way adults do.
Kids have a higher surface-area-to-mass ratio than adults, which means that in hot conditions — when the air is warmer than their skin — they actually absorb heat faster per pound of body weight. They also have lower sweat rates, so one of the body’s main cooling tools is less powerful in a small child than in a grown-up.
The science point that at “environmental extremes” — exactly the kind of heat waves that are becoming more common — children face a genuinely elevated risk of heat-related illness. Infants are the most vulnerable of all.
So as heat waves grow more frequent and intense, the shady side of the street stops being a matter of comfort and becomes a matter of safety — especially for the youngest members of the family.
There is ample science backing the reality that Planting trees can make your block/park/city dramatically cooler and safer this summer and in summers to come. It cannot, on its own, reverse climate change nor global warming at a global level but make it slightly more tolerable.
One more detail I found interesting: placement matters. The Cambridge team found that the *wrong* trees in the *wrong* spots can actually trap heat at night in some climates. The takeaway isn’t “plant anything, anywhere” — it’s “plant thoughtfully,” which is exactly why the organizations below are so valuable.
What you can actually do
The best news in all of this: adding trees is one of the rare climate-and-health levers an ordinary family can pull directly. Here’s where to start.
In the Los Angeles area:
- City Plants — If you live in the City of LA, you can request up to 7 free shade trees delivered to your door, or ask them to plant free street trees in the parkway in front of your home. It’s a public-private partnership with the city and LADWP that plants around 20,000 trees a year. (Note: this specific program is City-of-LA / LADWP-funded — neighboring cities like Santa Monica or Culver City run their own programs, so check with your city if you’re just outside LA proper.)
- TreePeople — A SoCal institution for nearly 50 years, with roughly 3 million trees planted. They host volunteer planting and tree-care events almost every weekend across the region, and events are explicitly family-friendly (kids 15 and under just need an adult along). If you want to lead a planting on your own street or local park, you can train as a **Community Forester** — email volunteer@treepeople.org.
- TREEAMS — A local, student-led movement (”Trees + Dreams”) born out of the 2025 Palisades and Altadena wildfires and developed in partnership with **Dr. Jane Goodall and the Jane Goodall Institute**. Founded by Margarita Pagliai of **Seven Arrows Elementary** ( our old elementary school, now based in Santa Monica), it’s mobilizing kids across 15+ LA schools to grow native trees in campus nurseries and replant them permanently in fire-impacted neighborhoods — with a goal of 5,000 trees. If you want your children involved in something hands-on and local, this one puts trees, kids, and community healing in the same place.
Anywhere in the U.S.:
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