Category Archives: Climate Change

Too Hot To Handle!

18 June 2024

When a heat dome persisted over the Central US. last August my reaction was “At least it isn’t happening here.” Well, now it is.

U.S. Day 3-7 Hazards Outlook for 20-24 June 2024 from NOAA Weather Prediction Center

A high pressure system that was overheating the Southwest moved in on Monday and put a cap over us that’s circulating hot air and trapping heat at the surface.

Diagram of a heat dome from Wikimedia Commons by NWS/NOAA

Meanwhile there are very few clouds to block the sun. It just keeps getting hotter and hotter. Climate Central says the metro areas of Indianapolis, Cleveland, Detroit, Pittsburgh, Philadelphia, Washington D.C., New York City, and Boston are experiencing:

  • Record high temperatures from 94°F to 99°F
  • High humidity that makes it feels hotter when heat index values reach 105°F
  • Nighttime temperatures never cool below the 70-76°F range.

Pittsburgh’s forecast is all orange.

Heat advisory forecast for 18-21 June 2024 (screenshot from NWS Pittsburgh)

Meanwhile all of us are under stress, especially plants, animals, outdoor workers, people without air conditioning and homeless people.

In addition to all the physical changes, heat makes us irritable, even angry.

Last evening severe thunderstorms knocked out power to more than 100,000 electric customers in southwestern PA. I’m fortunate to have both electricity and air conditioning so I’m staying indoors.

I can hardly wait for it to end.

p.s. US weather maps never show Canada. Did the heat just cease at the border? Nope. It’s hot in Canada, too!

Planted Them Weeks Ago?

Cherry tomatoes on the vine (photo from Wikimedia Commons)

27 May 2024, Memorial Day

Pittsburghers used to have a tradition that Memorial Day was the start of outdoor tomato planting season. But if you grow tomatoes today you know that’s not the case. You probably planted them weeks ago.

Just 50 years ago Pittsburgh had an annual average minimum temperature of -10 to 0 degrees F and those numbers didn’t change ten years after this USDA map was produced in 1960.

USDA Plant Hardiness Zone map, 1960

But the climate is changing rapidly now. Last year USDA officially revised their Hardiness Zones as shown on the 2023 map below.

USDA Plant Hardiness Zone Map, 2023

The Pittsburgh area shifted a 1/2 zone warmer in eleven years. Notice the paler color in the river valleys in Allegheny County on the zoomed map below. Our average annual lowest temperature used to be -5° to 0°F but it jogged 5 degrees warmer. Now it’s 0° to 5° F.

2023 USDA Plant Hardiness zones by zip code (zoomed out)

None of this is a surprise. We were certainly felt hot in April, the warmest on record.

Global temperature anomaly for April 2024 from

Air Pollution Makes Pollen Allergies Worse

Kentucky bluegrass, Poa pratensis, a common lawn grass in PA (photo from Wikimedia Commons)

23 May 2024

Talk about allergies! Oak tree pollen is finally diminishing in Pittsburgh, but grass pollen allergies are ramping up. I’m allergic to lawn grass. I feel it already.

Red fescue, a common lawn grass in PA (photo from Wikimedia Commons)

A study last year explained why we suffer more in the 21st century. Pollen season is getting worse every year because climate change is lengthening the growing season and increasing pollen production.

Unfortunately, a recent study explains that air pollution makes allergies worse. Pittsburgh has some of the worst particulate air pollution in the U.S.

“Plants that are grown in pollution-stressed situations are known to release more allergens,” says Elaine Fuertes, a research fellow at the National Heart and Lung Institute, Imperial College London.

Depending on the plant species, air pollutants can change the chemical composition of pollen, increasing the potency of pollen allergens and triggering stronger allergic reactions in people. …

…Air pollutants like particulate matter and nitrogen oxides may also make the exine — the outer coating of pollen grains — from some plant species more fragile and, therefore, more likely to rupture into smaller fragments that can penetrate deeper into the lungs.

Yale Climate Connections: Allergy symptoms got you down? Blame pollen AND air pollution.

Learn more about the interplay between pollen, air pollution and our allergies at Yale Climate Connections article below.

BONUS FACTLET: While looking for lawn grass photos I learned that Pennsylvania’s most common lawn grass, Kentucky bluegrass (Poa pratensis), is not native to Kentucky nor to North America. Poa pratensis is from Europe, North Asia and the mountains of Algeria and Morocco.

No Amount of Money Can Stop The Ocean

Protective dune washed away at Salisbury Beach, MA as seen 10 March 2024 (photo embedded from Salisbury Beach Citizens For Change on Facebook)

26 March 2024

A decades-old problem became acute his winter. After high winds and a historic high tide damaged 20+ beachfront homes in January at Salisbury Beach, Massachusetts, the residents took up a collection to build a protective dune. It took five weeks, 14,000 tons of sand and more than half a million dollars to build the dune to protect the homes. Three days later it was gone.

Completion of the dune project in early March brought high hopes to Salisbury Beach.

Facebook post by Salisbury Citizens for Change after the dune was completed on 6 March 2024

But in the next three days a natural occurrence, an astronomical high tide, washed it all away.

video embedded from WCVB Channel 5, Boston

The temporary dune did it’s job — no homes were damaged in March — but the idea of spending half million dollars after every storm is out of the question. So the town is regrouping and weighing options.

You might be wondering: Why don’t they just build a seawall?

Seawalls just move the problem a few hundred feet down the beach so they are generally not allowed in Massachusetts (see special exception in yellow).

screenshot from Questions and Answers on Purchasing Coastal Real Estate in Massachusetts at

Also, a seawall will remove the beach entirely as shown in this diagram. If Salisbury Beach builds a seawall they will have no beach at all, just a wall with a sheer drop to the ocean. Understandably, the homeowners want a beach.

Diagram by USACE via Questions and Answers on Purchasing Coastal Real Estate in Massachusetts

The ocean takes land slowly … and then all at once. No amount of money can stop it.

(credits are in the captions)

Will Spring Have a Setback This Weekend?

Coltsfoot closing at dusk, Schenley Park, 4 March 2024 (photo by Kate St. John)

7 March 2024

Two days ago it was so balmy in Pittsburgh that we wore T-shirts outdoors. The high on Monday 4 March tied the 74°F record, honeysuckle leaves popped out and I found coltsfoot blooming in Schenley Park. The week before was warm, too. Here’s what was blooming Feb 23 to March 1.

The weather is going to turn cold this weekend. Will spring be dealt a setback on Sunday?

In my city neighborhood Saturday night’s predicted low will be 35°F, still above freezing and significantly above normal. The map below shows the low temperature anomaly predicted for this Saturday (Sunday’s map won’t be available until tomorrow). Sunday’s forecast says it will go down to 30°F, barely below freezing.

Predicted low temperature anomaly for Saturday 9 March 2024 (map from Climate Central)

On Monday the weather warms up again. It’ll be 60°F on Tuesday.

I’m not too worried about a Spring setback in the City of Pittsburgh. NOAA’s March 2024 forecast looks pretty hot.

U.S. temperature outlook forecast for March 2024 (map from

(credits are in the caption)

Hot Weather Affects Maple Sugar Season

Maple sugar bucket hanging on a tree (photo from Wikimedia Commons)
Bucket collecting maple sap to make maple syrup (photo from Wikimedia Commons)

28 February 2024

The month of March is traditionally the best month for tapping maples to collect sap for maple syrup. The sap runs best with daytime temperatures above freezing and nights below freezing. When the days are too hot the sap becomes bitter. When the nights don’t freeze the sap stops running and the season is over.

This winter we’ve had yo-yo weather in the Northeast and Great Lakes states. You can see it in the forecast highs this week from Tuesday 27 Feb through Sat 2 March. The cold front coming through today will result in two nights below freezing. Then temperatures will rise again into the 60s. You can see the new blob of hot weather approaching from the Great Plains on Saturday 2 March.

Maple sugar farmers have had to adjust by starting the season whenever the sap runs — in Pennsylvania that might mean January — and pausing the season when the temperature goes up too high in hopes it will drop again.

This news article from Minnesota shows what their maple farmers are dealing with.

video embedded from KSPT5 Eyewitness News

Right Now You Can Kayak in Death Valley

Kayaking on Lake Manly in Death Valley (photo from Wikimedia Commons)

26 February 2024

In case you missed it …

During the Ice Age, the Pleistocene 2.58 million to 11,700 years ago, there was a lake 600 feet deep in Death Valley where Badwater Basin stands today. Named Lake Manly(*) by geologists, it disappeared 10,000 years ago.

Badwater Basin is 282 feet below sea level so any water that reaches it can only evaporate yet the evaporation rate is so high that the basin is a salt pan. Occasionally — decades apart — there’s enough rain to make a shallow lake.

Badwater Basin in normal times, Dec 2018 (photo from Wikimedia Commons)

In the past six months California has had two unusual rain events. On 20 August 2023 Hurricane Hilary dumped 2.2 inches and caused Lake Manly to re-form in place. (The deluge also closed the Death Valley National Park for two months.) Amazingly the lake persisted through the winter.

Lake Manly, Death Valley, December 2023 (photo from Wikimedia Commons)

And then the Atmospheric River event of 4-7 February dumped 1.5 more inches of rain. Lake Manly grew to a depth of 1 to 2 feet so in mid-February the National Park Service opened it to kayaking.

video embedded from Associated Press on YouTube

The last time the lake formed, in 2005, it lasted only about a week. This time NPS estimates it’ll be gone — or at least too shallow for kayaks — by April.

So if you want to kayak in Death Valley, get out there now before Badwater Basin returns to normal.

Lake Manly typically looks like this in Badwater Basin, (photo from 2010 at Wikimedia Commons)

Read more here at ABC News: An ancient lake has reemerged at Death Valley National Park.

p.s. From Wikipedia: “The lake was named in honor of William Lewis Manly, who rescued immigrants from Death Valley in 1849.”

Solstice Begins the Shortest Season

December sunrise in Pittsburgh (photo by Kate St. John)

21 December 2023

When the sun stands still tonight at 10:27pm Eastern Time we’ll experience the shortest day of the year and begin the shortest season as well.

Regardless of the weather we change seasons four times a year based on astronomical events: December solstice, March equinox, June solstice, September equinox. Since these events occur at the same moment everywhere on Earth, each of the four seasons lasts the same amount of time for everyone. This is easiest to see on the Seasons page at A screenshot of Pittsburgh at 6am today is shown below.

Current and next seasons in Pittsburgh before the winter solstice (screenshot from

If you don’t like winter, the Northern Hemisphere has the best arrangement. Our astronomical seasons from shortest to longest are:

  • Winter = 88 days, 23 hrs, 39 mins (shortest)
  • Autumn = 89 days, 20 hrs, 37 mins
  • Spring = 92 days, 17 hrs, 44 mins
  • Summer = 93 days, 15 hrs, 52 mins (longest)

Climate change guarantees that winter is the shortest weather season, too. Winter was 21% of the year in 1952 but will take up only 9% of the year by the end of this century.

Average seasonal lengths in Northern Hemisphere, information from

So I’m not counting on a white Christmas.

Read more about the weather-based lengths of the seasons at:

Getting Ready for More Landslides

Landslide by the Bridle Trail in Schenley Park, July 2019 (photo by Kate St. John)

12 December 2023

Spring is landslide season in Pittsburgh. Winter is a good time to get ready for it and there’s no time like the present. With climate change increasing Pittsburgh’s rainfall and downpours, our dissolve-in-water bedrock is getting wet faster.

This morning the Pittsburgh Post-Gazette reported that, thanks to a $10 million federal grant, the City of Pittsburgh is about to begin two landslide mitigation projects along city streets on Mount Washington and is putting a third one out to bid.

Thankfully there is money, though not a lot of it, for municipalities to prevent landslides on our roads, but if you live above a landslide and you own the land that slid you’re out of luck. The slide eventually takes your house with it.

video embedded from KDKA, April 2022

Pittsburgh is especially prone to landslides because of our geology.

Two natural conditions occurring in western Pennsylvania are most responsible for landslide problems throughout the area. First, in many places the bedrock consists mainly of shales and claystones. The primary culprit is a thick, 40- to 60-foot rock layer called the Pittsburgh red beds.

[Red bed]rock rapidly falls apart in water and tends to lose strength with each seasonal freeze-thaw and wet-dry cycle. Water that collects in the rock has little chance to drain and subsequently helps make the slope unstable from the inside out.

The second naturally occurring condition responsible for landslides is western Pennsylvania’s landscape, which is dominated by steep hills and valleys.

[Hillside] soils normally are stiff but very prone to downhill movement. This movement normally is imperceptibly slow. During the spring, however, the soil often becomes very wet from thawing snow and spring rains and the creeping can accelerate into a full-blown landslide.

Pittsburgh Geological Society: Landsliding in Western Pennsylvania

It is easy to find red bed outcrops on our hillsides. Here’s one in Schenley Park where there used to be topsoil but the red bed, formerly beneath the surface, eroded and left this tree on stilts.

Pittsburgh redbed rock eroded away from tree roots, Schenley Park (photo by Kate St. John, 2020)

A closer look at the red bed rock shows that it broke into tiny pieces — little crumbles — when it got wet. My foot is in the photo for scale.

Pittsburgh redbed rock crumbles into tiny pieces when wet (photo by Kate St. John, my boot shown for scale)

The location of these photos is marked on a Google topo map of Schenley Park below. Notice how steep the hillside is where the red bed is exposed. Uh oh!

Schenley Park topo map with arrow pointing to location of redbed photos (map screenshot from Google Maps)

Because of the prevalence of Pittsburgh red bed rock there are landslide problems throughout Allegheny County. Click here or on the map image below to see the details. Keep in mind that the colors red and orange are bad. The only safe color is yellow.

screenshot of Allegheny County from the Allegheny County Landslide Portal

And just for emphasis, check out this video of a house that slide down the hill in 2019.

video embedded from WTAE Pittsburgh on YouTube, 22 Feb 2019

El Niño Snows in DC But Not Pittsburgh

Snow on sweetgum seed balls, 17 Dec 2020 (photo by Kate St. John)

27 November 2023

Last week a friend remarked on the wide variety of winter forecasts being touted for Pittsburgh from “Swamped With Snow” to “No Skis in Our Forecast.” How could the predictions be so different? I think it’s the Beltway effect.

Right now the world is in an El Niño year of warm sea surface temperatures in the central and eastern Pacific at the equator and along the coasts of Ecuador and Peru.

Sea surface temperatures during 1997 El Niño (map from Wikimedia Commons)

According to Wikipedia, this warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia, India and northern Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean. El Niño seriously affects South American weather and ripples out to North America as well. The U.S. seasonal outlook, Dec 2023 to Feb 2024, shows higher temperatures in the north and wetter weather in the south this winter.

Seasonal temperature and precipitation outlooks for the U.S., Dec 2023-Feb 2024 (maps from NOAA)

Of course this affects snowfall. El Niño’s winter history in 1959-2023 shows more snow in some places (blue color) and a lot less in others (brown color). Interestingly, Pittsburgh is in the Less Snow category while Washington, DC has More Snow than usual.

Snowfall during all El Niño winters (January-March) compared to the 1991-2020 average (after the long-term trend has been removed). Blue colors show more snow than average; brown shows less snow than average. NOAA map, based on ERA5 data from 1959-2023 analyzed by Michelle L’Heureux.

News organizations have a big presence in the DC Beltway area and write stories for the region. Some weather stories originate there and cross the Appalachians but when the news gets to Pittsburgh it might not apply to us. The typical example is when 2 feet of snow are forecast for D.C. and hardly any falls here. I think of this as the (DC) Beltway news effect.

So when we hear dire predictions for Pittsburgh’s winter this year I plan to wait rather then worry. My guess is that we’re likely to have rain.

Raindrops on twig (photo by Kate St. John)

I sure hope the temperature doesn’t hover near freezing when it rains. Fingers crossed that we’ll be fine.

Glaze ice in Pittsburgh (photo by Kate St. John)

Read more about snow and El Niño at NOAA’s S(no)w pain, S(no)w gain: How does El Niño affect snowfall over North America?