Category Archives: Weather & Sky

Variably Cloudy

Sunrise on 31 July 2022 (photo by Kate St. John)

5 August 2022

This week the clouds at sunrise varied from brooding horizontal stripes to dramatic ragged puffs.

Sunrise on 4 August 2022 (photo by Kate St. John)

This tall stack presaged scattered thunderstorms though none had been predicted.

Cloud stack on 4 August 2022 (photo by Kate St. John)

Twice this week isolated rain clouds created spectacular rainbows half an hour before sunset. This one on 4 August has a faint second rainbow above it.

Rainbow(s) on 4 August 2022 (photo by Kate St. John)

On 1 August the pot of gold was in Shadyside.

Rainbow on 1 August 2022 (photo by Kate St. John)

(photos by Kate St. John)

Wrapping Up July

St. John’s wort on the South Side, 17 July 2022 (photo by Kate St. John)

30 July 2022

Wrapping up July …

St. John’s wort’s yellow flowers always attract my attention because the plant shares my name. Find out what’s in the name in this vintage article from 2012.

This month I learned that chicory flowers (Cichorium sp) last only one day. On a foggy morning I found this one, barely open and doomed to wilt by afternoon. Learn more at #bioPGH Blog: Chicory, Dickory, Dock – The Flowers are on the Clock.

Chicory opening on a cloudy morning, Schenley Park, 22 July 2022 (photo by Kate St. John)

We had several spectacular sunrises in July, especially this on the 17th.

Dawn on 17 July 2022 (photo by Kate St. John)

Soon we’ll say good morning to August.

(photos by Kate St. John)

Summer Snowflake

Queen Anne’s Lace, Schenley Park, 22 July 2022 (photo by Kate St. John)

23 July 2022

The flowers on Queen Anne’s lace (Daucus carota), or wild carrot, are so lacy and regular that they resemble snowflakes when viewed from above, especially in black-and-white.

Queen Anne’s Lace, black-and-white (photo by Kate St. John)

Look closely and you’ll see that the tiny flowers inside the umbel have 5 regular parts. Step back to see the pattern of 5’s replicating to the edge.

Queen Anne’s lace umbel is 5-sided (photo by Kate St. John)

Unlike winter’s 6-sided snowflakes (below) these summer “snowflakes” have only five.

Snowflake (photo by Alexey Kljatov via Wikimedia Commons)

p.s. See Vicki Dinsmore’s comment below about wild parsnip which is not the same thing!

(photos by Kate St. John and from Alexey Kljatov via Wikimedia Commons)

So Hot. Getting Hotter

22 July 2022

This week has been and will be unusually hot around the world. On Tuesday in Britain, where there is virtually no air conditioning, the high temperature was a record-breaking 40.3 degrees Celsius, 104.5 degrees F! It was as hot as Phoenix, Arizona without the respite of air conditioning and community cooling centers.

Red sun through smoke of the Woolsey Fire, California, 9 Nov 2018 (photo from Wikimedia Commons)

Back in the 1970s and 1990s climate change was slow to ramp up so we fooled ourselves by saying (1) Nothing’s changed yet so it’s not going to change, and (2) Climate change will be manageable because it won’t happen fast.

Wrong on both counts. This animation from NASA Goddard Institute of Space Studies shows world temperature anomalies in Fahrenheit, 1880 – 2021. The fastest changes have occurred in the last 5-10 years!

Temperature anomalies in Fahrenheit, 1880-2021 (from NASA, Goddard Institute of Space Studies)

So hot! And getting hotter.

(photos from Wikimedia Commons, animation from NASA Goddard Institute of Space Studies)

Seen This Week and Last

Deptford pink, Butler County, 10 July 2022 (photo by Kate St. John)

16 July 2022

Flowers are blooming, fruits are ripening and the sky has been spectacular. Here are just a few things seen outdoors this week and last.

  • Deptford pink’s (Dianthus armeria) small flower, at top, is worth a closer look. Native to Europe it does well in North America but is disappearing from the UK.
  • Enchanter’s nightshade (Circaea canadensis) was in bloom last week in Schenley Park, shown below.
Enchanter’s nightshade in bloom, Schenley Park (photo by Kate St. John)
  • Spotted wintergreen (Chimaphila maculata) is blooming in Butler County. This plant goes by several names including “striped wintergreen.” Here’s why it is not pipsissewa.
Spotted wintergreen, Butler County, PA, 10 July 2022
  • Wineberry fruits (Rubus phoenicolasius) are ripening in Frick Park. This shrub was introduced from Asia as breeding stock for Rubus cultivars in 1890 but it grows so vigorously that it’s now invasive in Pennsylvania. Unlike native raspberries, wineberries are sticky to the touch. They taste well enough when you eat them in the woods but are boring on cereal. I tried.
Wineberry, Frick Park, 14 July 2022 (photo by Kate St. John)
  • Bottlebrush buckeye flowers were at their peak last week in Schenley Park. This closeup shows the feathery stamens.
Bottlebrush buckeye, closeup of flower, 8 July 2022 (photo by Kate St. John)
  • And finally, we’ve had some spectacular sunrises in the past two weeks. A deep blue sunrise on Wed 6 July (below) and a fiery orange one on the 8th. Click here to see the fiery sunrise.
Sunrise in Pittsburgh, July 2022 (photo by Kate St. John)

(photos by Kate St. John)


Wilted white snakeroot at Schenley Park, 4 July 2022 (photo by Kate St. John)

9 July 2022

Hot dry weather since early June has turned the grass brown and caused low water in Pittsburgh area streams. By the Fourth of July leaves were wilting in Schenley Park and Little Sewickley’s creek bed was exposed at Sneed’s.

Low water exposes the creekbed of Little Sewickley Creek at Sneeds, 4 July 2022 (photo by Karyn Delaney)

Precipitation had changed in only five weeks from 1.20 inches above normal at the end of May to -1.58 inches below normal on 4 July. A thunderstorm on 6 July reduced the deficit to -1.24 inches below normal this morning. (See statistics at the NWS Pittsburgh Local Climate page.)

Are we in a drought?

Not really. Despite wilting leaves this week’s U.S. Drought Monitor map puts most of Pennsylvania in the normal range. (S=short-term impacts, L=long term impacts)

U.S. Drought Monitor map, 5 July 2022 (map from US Drought Monitor at UNL)

The Drought Severity Index (Long Term Palmer) map, below, is both predictive and more fine grained. It shows a hint of drought in four southwestern Pennsylvania regions (pale yellow) and extreme drought in the U.S. West and Southwest (orange). The surprise to me is the extreme long term drought in eastern North and South Carolina, evident on both drought maps. Northeastern North Carolina needs 12 inches of rain to get back to normal (click here for the map).

Long Term Palmer Drought Severity Index by county (map from NOAA Climate Prediction Center)

It’s reassuring to know that Pittsburgh is not heading for severe drought. I feel bad for all the areas colored scary red and orange.

(photos by Kate St. John and Karyn Delaney, maps from US Drought Monitor at UNL and NOAA Climate Prediction Center)

Lightning and Fish

Lighting strikes as the USS Abraham Lincoln transits the Strait of Malacca (photo from Wikimedia Commons)

6 July 2022

When a thunderstorm approaches at the beach or a swimming pool, the lifeguards tell everyone to get out of the water. Lightning often strikes water and anyone in it can be electrocuted.

Fish live in water so why don’t they die from lightning? The National Weather Service explains:

Before a lightning strike, a charge builds up along the water’s surface. When lightning strikes, most of electrical discharge occurs near the water’s surface. Most fish swim below the surface and are unaffected.

National Weather Service: Lightning and Fish

This NWS animation shows the positive charge building on the surface and the negatively charged lightning strike spreading horizontally. Fish swim below it all.

Humans swim on the water’s surface where lightning has its greatest effect. In addition, lightning is a hazard in open outdoor spaces like beaches.

West Beach Galveston, 1973 (photo from Wikimedia Commons)

Interestingly in the US, the most dangerous activity during lightning is fishing; beaches are second. We thought golf was the worst but it is far down on the list.

US lightning death statistics by activity, 2010-2021 (table from National Weather Service, Paducah, KY)

During a thunderstorm the fish are safer than the fisherman.

(photos and animations from Wikimedia Commons; click on the captions to see the originals)

Hurricane Agnes, 50 Years

Flooding in Elmira, NY from Hurricane Agnes, 1972 (photo from

22 June 2022

Pittsburgh is 300 miles from the Atlantic Ocean so the hurricanes that pass over us are not even tropical storms by the time they reach southwestern Pennsylvania. We usually don’t know the names of the remnant hurricanes that bring us rain but there is one that lives in infamy. Fifty years ago this month Hurricane Agnes devastated Pennsylvania, New York, Maryland and Virginia.

In June 1972 I lived with my parents and worked in a restaurant in the South Hills of Pittsburgh. I remember the heavy rain that soaked me during my few steps to the car when my mother picked me up at work. Our neighborhood was not flooded but Downtown Pittsburgh was.

Hurricane Agnes flood in Pittsburgh, June 1972 (photo linked from

“The Agnes flood crested at 35.85 feet in downtown Pittsburgh, eleven feet above flood stage. The US Army Corps of Engineers estimated it would have topped 47 feet if not for the flood control dams and reservoirs, built since 1938, that held back much of the water. East Branch on the Clarion River was more than full. Kinzua Dam in Warren, PA was within three feet of the top. Tygart Reservoir in West Virginia was 85% full. Other dams stored water at 90% capacity.” — paraphrased from Flood of 1972 at

Pittsburgh was fortunate to receive a fraction of the rain that fell in the Susquehanna River watershed. More than 10 inches fell in much of east-central Pennsylvania, reaching a maximum of 19 inches in western Schuylkill County.

Track of Hurricane Agnes and rainfall totals for the storm, June 1924, 1972 (map from NOAA)

Many Pennsylvania towns were ravaged, including Harrisburg.

So was the Southern Tier of New York, as shown in this 2018 video about Elmira.

That September I returned to college in Geneva, NY and joined a crew of volunteers doing flood relief work in Horseheads, NY, six miles from Elmira. Our job was to remove mildewed interior walls in a house flooded by Newtown Creek during Agnes. The owners were living in a disaster-relief trailer in the backyard and hoped to rebuild their house.

It was a lesson in empathy. The walls were plasterboard on studs, just like those in my parents’ house. We broke the plasterboard and levered it off with crowbars. It could have been my own home that I was taking apart and my own life upended by the flood. I felt very lucky.

Read more about Hurricane Agnes at:

p.s. This 10-minute archival video shows Corning, NY in June 1972 before and after the flood. It includes flood relief efforts like the work we did in Horseheads.

(photos and maps from the NOAA / NWS, Pittsburgh flood photo embedded from Click on the captions to see the originals)

Weird Clouds: Mammatus

Mammatus clouds over Pittsburgh, 16 June 2022, 9:00pm (photo by Kate St. John)

17 June 2022

Severe thunderstorms were predicted for 6:00pm yesterday in the upper Ohio Valley. By 2:00pm the Severe Thunderstorm Watch called for an inch of rain in 1 hour — definitely flash flood material — but at 5:00pm the storm line split. Some went north toward I-80, the rest went south to West Virginia. Pittsburgh had no lightning, no strong winds, no rain. Nothing happened.

But the sky got weird. At sunset the last of the storm clouds left our area with a flourish of rare mammatus clouds, dramatically lit from below. Their name is derived from the Latin word for breast or udder.

As Wikipedia explains, mammatus are formations that hang from the base of rain clouds. The distinct lumpy undersides are formed by cold air sinking down to form pockets. Usually composed of ice, each lobe averages 1/2 to 2 miles across and 0.3 mile deep. Alone a lobe can last 10 minutes but a cluster may last several hours.

Mammatus are an indication of a severe thunderstorm but in my experience in Pittsburgh they do not predict the storm. Instead they show up after the storm has passed.

The clouds started out as lines and gave way to stratus clouds and a gleam at sunset.

Mammatus clouds forming lines, Pittsburgh PA, 8:58pm, 16 June 2022 (photo by Kate St. John)
Mammatus clouds looking east, Pittsburgh PA, 8:58pm, 16 June 2022 (photo by Kate St. John)
Last line of mammatus clouds gives way to stratus at sunset, looking west, Pittsburgh PA, 9:05pm, 16 June 2022 (photo by Kate St. John)

Next time you see these weird clouds, remember their name describes their shape.

p.s. Steve Tirone left a comment with a link to his video of the clouds.

(photos by Kate St. John)

What’s Your Wind Rose?

Detail of a windrose on a plaza in Portugal (photo from Wikimedia Commons)

16 June 2022

If you live in a windy place, the trees lean away from the prevailing wind.

Trees shaped by the prevailing wind (photo from Wikimedia Commons)

To see this effect on paper meteorologists create a wind rose that graphs the wind’s direction and speed over time. The petals indicate the percentage of wind from each direction. The colors show the speed. The center is calm. Let’s look at some wind roses from Iowa State’s Iowa Environmental Mesonet.

Though Pittsburgh is not a particularly windy place our 50-year wind rose (1970-2022) indicates our prevailing wind from the southwest. 10.9% of the time there is no wind at all.

In places where wind is not obstructed, such as the coast and the Great Plains, wind roses are lopsided. This map shows the locations of three extreme wind roses displayed below.

USA map of states with list of windrose cities at the links below (original map from Wikimedia Commons)
Miami, Florida windrose from Iowa Environmental Mesonet
Wichita, Kansas windrose from Iowa Environmental Mesonet
Los Angeles, California windrose from IEM

Here are some more from Iowa Environmental Mesonet. Click the links.

What’s your wind rose?

Retrieve it here.

  1. Visit Iowa State’s Iowa Environmental Mesonet Site Locator.
  2. Select by Network: Drop down to pick your state ASOS network, for example: “Ohio ASOS”. Click on [Switch Network]).
  3. Then Select by Station (drop down to pick your local weather station, for example “Toledo” and click on [Select Station].
  4. Click on [*Wind Roses], the 9th of 13 buttons.

(images from Wikimedia Commons and Iowa Environmental Mesonet; click on the captions to see the originals)