Meteorological Summer 2023 By The Numbers
By Ryan Knapp, Weather Observer/Staff Meteorologist
Looking at our calendar, we are only days away from autumn which will land on Saturday, 23 September 2023. This date refers to the astronomical autumn season, which is based on Earth’s tilt on its axis as it is orbiting around the sun. Therefore, the seasons of autumn and spring would land on the equinoxes (when day and night are roughly of equal length) and summer and winter would land on solstices (when day/night are of their greatest lengths, longest day in summer, longest night in winter). However, for those of us studying weather/climate, we are already in an autumn frame of mind.
Meteorological seasons typically occur three weeks earlier than astronomical seasons. Meteorological seasons are based on the annual temperature cycle – winter is cold, summer is warm, and fall/spring are the transition between the warmth and cold. So using the annual temperature cycles, meteorological autumn would be Sept, Oct, and Nov (winter – Dec, Jan, Feb; spring – March, April, May; and summer – June, July, August). Meteorological autumn therefore occurred 1 September 2023 and will run until 30 November 2023. Why do meteorologists and climatologists do this? This is done for consistency – by dividing up the seasons by calendar dates they are nearly even varying between 90 to 92 days. And the other reason is for less variation between seasonal and monthly statistics from year to year.
No matter which fall you choose to recognize and/or celebrate, the key thing to remember is that September is the start of our transition season from summer into winter which means that our warmest weather is generally behind us, more icy/snowy weather lies ahead (we received our first few flakes of the season in late August), and winds start to roar back to life as stronger pressure gradients develop (by October, statistically speaking, 1 out of every 2 days will see hurricane force winds and 1 out of every 4 will see gusts of 100 mph higher). So, make sure to check out the Higher Summits Forecast so that you are prepared for whatever the mountain might throw your way.
While meteorological fall has arrived, I figured it might be worthwhile reflecting back on meteorological summer 2023. Looking back at weather stats, if I had to summarize summer 2023 weather conditions on the summit, they would be – rainy, snowy, foggy/cloudy, and “calm”. To find out why these words were chosen, let’s look back at some of the stats from last year:
In terms of total liquid precipitation, from 1 June to 31 August 2023, the summit of Mt Washington received 48.39 inches, which was 23.15 inches above the 1991-2020 30-year normal for our location. This makes summer 2023 our second wettest season in our dataset (1932-present) behind the wettest season which is winter (Dec-Jan-Feb) 1969 when 50.26 inches of precipitation was collected. June 2023 was the 2nd wettest June in our dataset with 17.30 inches falling. July 2023 was our wettest July in our dataset with 17.08 inches falling. And August 2023 was our 2nd wettest August in our dataset with 14.01 inches falling.
From 1 June to 31 August of 2023, the summit received 8.4 inches of snow, which was 7.0 inches above the 1991-2020 30-year normal for our location. While a trace of snow fell in August 2023, the rest fell in June with that 8.4 inches in June making it the snowiest June ever in our dataset.
Our average summer temperature for 2023 was 47.8°F (8.8°C), which is 0.2°F below the 1991-2020 30-year normal for our station. When broken down by months, June was a cool month as it was 0.8°F below the 1991-2020 30-year normal for our station. July was a hot month as it was 2.8°F above the 1991-2020 30-year normal for our station. As such, July 2023 wound up being our 7th warmest July in our dataset and the 8th warmest month ever in our dataset. August on the other hand was 2.6°F below the 1991-2020 30-year normal for our station. As such, August 2023 wound up tying for the 14th coolest August in our dataset. Our warmest temperature recorded in summer 2023 was 66°F (18.9°C), which occurred on July 6th. Our coldest temperature recorded in summer 2023 was 26°F (-3.3°C), which occurred on June 4th.
In terms of winds, for summer 2023 our average was 23.5 mph, which was 2.1 mph below the 1991-2020 30-year normal average for our location. Of note was June 2023 which was our 3rd least windy (or “calmest”) June in our dataset and was the 11th least windy (or “calmest”) month ever in our dataset. Our highest gust recorded for summer 2023 was 94 mph, which occurred on August 19th. From 1 June to 31 August 2023, we had 10 days which had gusts of 73 mph or greater and of those days, 0 days had gusts that were 100 mph or greater.
As for our weather during 1 June to 31 August 2023, we averaged 24% of the possible sunshine. The summit had 0 days (sunrise to sunset) that were noted as clear or mostly clear, and there were 8 partly sunny days, with the remaining 84 days being filed under mostly cloudy, cloudy, or obscured (fog). We had 88 days with at least some amount of fog recorded during a 24-hour period. We had 70 days with rain and 10 days with snow.
Late summer sunrise looking down the Mt. Washington Auto Road at the summit.
Ryan Knapp, Weather Observer/Staff Meteorologist