Really weird... the thing with almost frost in places outside of Stockholm. While the West coast of South Sweden had like 16°C. Even places like Åland, Marihamn Airport, which lies between Sweden and Finland, right at the sea (11.6°C water temperature) - but reported only +1°C already at midnight.
Or the small island of Adelsö in the Mälaren lake, just west of Stockholm... reported 1.7°C, despite the lake measuring 12-13°C in the water. Around 23:00 it went from +10.6°C to only +3.5°C in just ONE HOUR.
I find that rather unusual, if you ask me...
Well, and Tullinge SW of Stockholm - 7 km from my place, reported -0.7°C at the lowest point this morning.
Tullinge station history
Well, i had to study for several hours the history of Tullinge Station, since 1955, in order to determine how often this has happened before. From emotion to analysis. In fact, frost temperatures happen occasionally there in June. The lowest measured temperature there in June, was in 1955 with -3.6°C, and in the morning of 21 June 1959, it reached -2.5°C.
The latest date of frost ever having occurred was on a 22 June 1975 with -0.1°C.
10 June 2023
-1.2 in Tullinge, -0.7° Arlanda Airport
We continue. As on the next morning, apparently another "pseudo" coldfront had gone down, albeit without any whistles or bells, practically without or barely any clouds... but boy it went cold over East Svealand / Stockholm region, but also over Southern East Sweden inland...
Here below you see the low temperatures in the morning of 10 June 2023, at around 04:00 - showing how cold east middle Sweden turned right before sunrise. Notice that in Gothenburg at the same time you found temperatures ranging between 13°C and 15°C.
A remarkable difference.
The average MIN in Tullinge outside of Stockholm this time of the year lies 10.1°C higher (= 8.9°C) ... Just saying.
11 June 2023
-0.3°C Svanberga, -0.2°C Eskilstuna, +0.1°C Tullinge
Again some places reported frost or near frost temperatures. Of course, Tullinge was one of those stations.
Stockholm-Tullinge Station • 1955-2020
I made these charts because I wanted to know, how often this strange frost happens so late being almost mid June now. So, I had to check this periods (days before and after today's date), in order to see how common or uncommon the phenomena of extreme late frost appears at Tullinge station.
Below you see MINIMA temperatures registered between year 1955 and 2020 between 6-15 June. All in one, so to speak.
We have to go back to June 2009 in order to find an equally low temperature of -1.2°C. And before that it was in June 1984 with -1.5°C.
Frost happen rarely in June - but it has happened
Based on the same data, you can see below the "distance" between frost events. As well the annual range of MIN temperatures for each 6-15 June period every year (except the period of 1985-95, and 2004 which are missing).
The HIGHEST MIN ever to have occurred in that 10 day period of June, was a very mild +16.6°C (June 2008). Well and already mentioned before, the coldest MIN was -3.6°C - which also is the absolute June cold record for the station.
Urban Heating Island Effect
Greta's scaring "Global Warming"
I looked at the differences between STOCKHOLM CITY and TULLINGE. The latter representing the largely unaffected country side 19 km outside of Stockholm (and 7 km from my place). The CITY CORE of Stockholm the Urban Island Heating effect.
Stockholm City vs Tullinge
Let's first look at the respective MINIMUM temperatures this year:
In the chart above, you can clearly see, that STOCKHOLM CITY is almost always warmer compared to Tullinge station. Almost never the other way around. And when it happens, the differences are rare and minimal.
The difference between both places can go beyond 10°C or more, with Stockholm being so much warmer at night compared to Tullinge. The Heating Island Effect is really pronounced, even in a place like the Swedish Capital vs country side.
The total average (1 Jan - 10 June 2023) is +3.71°C warmer in the City core compared to country side. For the whole of year 2022, it was +3.55°C.
Differences of MAXIMA
Stockholm City vs Tullinge
Now let's look at the PEAK (MAX) temperatures differences between STOCKHOLM CITY and TULLINGE station. And the differences are most of the time very small.
In average only +0.60°C warmer in the city compared to Tullinge. A few times it happens that Tullinge get to be every so slightly warmer in max temperatures - but most often, both places are pretty similar - which is interesting, given that this rather weak "urban island effect" barely occurs during winter.
Why is that ? Good question - I don't know.
In the chart below, you can clearly see, that STOCKHOLM CITY is almost always warmer compared to Tullinge station. When that happens, the differences are really small.
Most warming effect / dramatic temperature differences - we see during nights.
When I look at Tullinge station minimum temperatures in general (not shown here), I can sometimes get the feeling of that there is a cooling trend going on (when comparing with it's normal average MIN). This is not written into stone, because determining such things require deeper comparisons and pondering.
Due to the City Core Heating effect, such trends I do not see in Stockholm City. It always seem to overlay any useful tendencies regarding warming or cooling. It often looks like a continues warming trend. While Tullinge appears to be more truthful - revealing warming or cooling trends better because it isn't affected by artificial heated temperatures like Stockholm City.