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.
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.
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.
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.
“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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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 timeanddate.com. A screenshot of Pittsburgh at 6am today is shown below.
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.
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.
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!
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.
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.
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.
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.
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.
Once a decade USDA crunches the past 10 years of actual temperatures across the U.S. to calculate the growing season for each location. What they found this time is that 2010-2020 was so much warmer that the plant hardiness zones moved north. Again.
In Pennsylvania we lost our coldest zone and gained a warmer one. The Average Annual Extreme Minimum Temperature — the worst freeze that can happen to a plant — used to be -20 to -15 F (Zone 5a) in Warren and McKean Counties. Both lost that colder zone and parts of Warren jumped two zones.
Meanwhile, southeastern Pennsylvania’s temperature span rose 5 degrees and jogged the Philadelphia area out of 7b into Zone 8a. That means you can grow some pretty exotic stuff in Philadelphia now.
NPR interviewed Megan London, a gardening consultant from Hot Springs, Arkansas whose region made the same jump as Philadelphia.
In the new map, London’s region in central Arkansas has moved from zone 7b to zone 8a. What that means for her is that she’s now considering growing kumquats, mandarin oranges, and shampoo ginger, a tropical plant.
