Interpretation of the logger’s graph (using LogTag Analyzer 3 software)
First day (July 17)
Hiking under a sunny sky I reached the research area before noon. The weather station started its operation at 12:11 PM when the screen of the logger showed 37.7 degrees Celsius. As I set the device for 1 minute logging (short intervals) the curve has the typical “saw aspect” with many small ups and downs inside the general “big waves”.
Until 1:53 PM the temperature climbed to 40.9 degrees, then at 3:13 PM reached the day’s maximum: 41.1 degrees Celsius. I left the installation before 5 PM when it was still slightly above 40 degrees and returned here only in the last day (21th July) to collect the equipment. During my staying the sky was completely clear with some short term wind speed intensifications.
The graph shows that a more abrupt descent started at 7:15 PM in the evening when the temperature dropped from 37.2 C to 22.1 C until 5:02 AM. Afterwards there is an anomalous rise to 29.5 C until 6:20 AM, followed by a secondary morning drop to 23.8 C at 7:03 AM, certainly caused by wind.
Second day (July 18)
This was the hottest day. The temperature exceeded 40 degrees at 12:06 PM and continued to rise until 2:52 PM when the highest value of the 5 days research was recorded: 42.2 degrees Celsius. The 40+ heat was present until 6:30 PM and the more abrupt descent started at 7:51 PM when dropped from 37.8 C to 26.3 C until 10:55 PM.
The next 20 minutes represents the biggest anomaly of the entire measuring period as until 11:18 PM the temperature rapidly climbed back to 34.5 degrees, maintaining the unusual warmth until 2:07 AM in the night when still were 32.6 degrees. Afterwards dropped to 26.6 C until 2:55 AM, but then raised again to 33.5 C at 5:31 in the dawn. Very chaotic night pattern for sure.
I was in the Mani peninsula at Kyparissos at that time and measured an unusually high 34 degrees around 7:30 in the morning. As I observed no clouds at all in all directions, there is no doubt that all these extreme fluctuations were caused by wind.
Third day (July 19)
Another very hot day. Reaching 40 degrees before 12:30 PM, the temperature was rising until 3:08 PM when 41.8 degrees Celsius, the day’s maximum and the second highest value of the research was registered. It remained above 40 degrees until 6:06 PM, while a more abrupt descent started after 8:30 in the evening when dropped from 35.3 C to 29.3 until 9:26 PM.
Then a very similar to yesterday’s “out of the nowhere” kind of rise happened, thus in only a few minutes it warmed back to 33.8 C. Following another two sharp ups and downs during the night, it cooled down to 26.2 C until 1:20 AM, only to climb back again to 31.5 degrees at 6:37 in the early morning. I was in the cape Tenaro area during this time and experienced constant hot and sunny weather with mild to moderate wind.
Fourth day (July 20)
Generally, the temperature was steadily rising from the morning until 1:54 PM when the peak of the day, 41.2 degrees Celsius was registered. With a few drops between, this value was reached again at 2:29 PM. It went below 40 degrees after 4 PM and this time the night cooling has a more typical aspect, without the extreme fluctuations like in the case of the previous two.
The minimum of the morning and also the lowest temperature of the research was 21.7 degrees Celsius, registered at 6:43 AM. Still in southernmost Mani, I measured below 25 C on the balcony of my room in Palyros village, definitely cooler than the previous morning when it was around 28 degrees. The sky remained completely clear day and night.
Fifth day (July 21)
Today I traveled back to collect the measuring equipment, reaching the area of the research around 3:30 PM. It was less hot than in the previous days, both in Gytheio and here in the Evrotas valley. I observed cumulonimbus clouds above the Taygetus mountains, but except that the sky remained completely clear.
The graph shows that after a peak of 35.8 degrees Celsius at 12:25 PM the temperature entered a slow descent phase reaching 33.8 C at 2:24 PM (probably sea breeze), then stabilizing more or less around 35 degrees. Observing the constancy of the milder conditions I stopped the data logger after 4 PM.
The average maximum temperature of the five days research period is 40.4 degrees Celsius, while the average minimum of the four nights between is 24.1 degrees Celsius, giving a mean daily amplitude of 16.3 degrees. The biggest daily fluctuation was 20.1 degrees and happened on the second day when the temperature raised from 22.1 to 42.2 degrees Celsius.
General conclusions
- The sky is usually clear both day and night, convective clouds can appear mostly only above the taller mountains.
- The temperature rise during the daytime is quit regular, typically reaching the maximum around 2-3 PM, but sometimes is affected by the sea breeze, which can stop the rise earlier.
- The late evening and night hours can have a very chaotic course with significant fluctuations in very short periods of time due to local föhn winds, which easily disrupt the nocturnal cooling of the valley.
- The daily amplitude is medium to high (14-20 degrees) facilitated by the subtropical latitude and very dry conditions, but limited by the earlier mentioned fönh winds.
- The short time temperature fluctuations are much bigger during the dark hours, reaching 8 degrees in 20 minutes.
Comparison with the hottest areas of Greece and Europe
According to Ogimet, two greek weather stations exceeded the maximum recorded by my installation in the gorge of the Evrotas river. These are Serrai (Serres) and Kalamata. The former is situated in the north of the country and due to its more inland location it is indeed often very hot, likewise Demir Kapija and Gevgelija in nearby North Macedonia or Sandanski in south-western Bulgaria.
This summer’s heatwave was especially strong in the central and northern Balkans including the country I live, Romania. In these areas the thermal anomaly reached or exceeded 10 degrees sometimes, thus the usually hotter Peloponnese had a hard time keeping up with the northern neighbors sitting right under the center of the heat dome. More stations in Romania, including the capital București reached 40-41 degrees, while northern Macedonia exceeded even 42 degrees Celsius in this period. Albania, Serbia, Moldova and Ukraine also went above 40, breaking or approaching the older records.
(the date on the image refers to the previous 24 hours)
Kalamata (known for its tasty olives) is situated in a protected bay of the southern Peloponnese, which likely experiences the hottest weather during strong north-eastern föhn effect, when the wind is blowing across the Taygetus, annihilating the sea-breeze. I checked the Ogimet statistics (see the chart below) and yes, that was the case, during the hotter part of the day the wind was coming across the high mountain.
We have to mention here that Greece has two different weather monitoring networks: one of them is the HNMS (Hellenic National Meteorological Service), which uses passive solar radiation shields and the other is the NOA (National Observatory of Athens), which uses fan aspirated ones instead. The stations appearing in the Ogimet statistics are from the HNMS, thus the ones with classical multi-plate shields.
At the present moment it’s well documented that during strong solar radiation with little wind the passive shields can’t protect the thermometer’s sensor from overheating as efficiently as the fan aspirated versions and are outperformed also by the helical Barani shield, the one which I am using. More than that, I heard a local specialist mentioning that there is a huge discrepancy specifically between the two weather stations (HNMS vs NOA) of Serres city, the one using passive shield having a higher average maximum in the summer with up to 2 full degrees (!), which backs up my intuitive skepticism regarding the “sticking-out nature” of the related Ogimet statistics.
Note: This part will remain open for update in case of obtaining some valuable info regarding the measurements of the two hellenic weather networks. I am especially curious of the NOA statistics of the hottest stations during the 17-21 July interval. Until now I found a single one, which is that the messenian Skala village (north of Kalamata) measured the highest temperature in Greece and that’s 43.1 degrees Celsius. This is interesting as conflicts with the slightly higher value of Serres appearing on Ogimet. Let’s wait for the clarifications.
*Update on 5th September 2024:
Thanks to a local specialist I received complete monthly data sets, which are more than interesting in the context of my own measurements (see the charts below with the 5 related maximums inside the red rectangles):
And below are the extreme values recorded at my location:
What can we conclude from this?
In a nutshell: I have to correct my less optimist previous statement (read the last chapter) regarding the thermal advantage given by the small scale topography, as my location seems to be hotter with over 1 degree than both Sparti and laconian Skala settlements (which are pretty close to each other for that matter). The exception is the last day (21th July) when the breeze affected the lower course of the Evrotas but not the more inland located Sparti city.
More concretely: On 18th July (the hottest day at my weather station) the advantage was 1.8 C over Skala NOA, 1.6 C over Sparti NOA and 2 full degrees over Sparti HNMS meteorological station. The average advantage for the four hotter days is 1.4 degrees over both Skala NOA and Sparti NOA and 1.5 degrees over Sparti HNMS station. Taken into account the relatively small distances inside the same basin and the fact that my research spot is located between the two settlements we can assume that the obvious positive gap can’t be accidental.
-end of update-
Could the Evrotas gorge be the hottest place in Greece?
I think the correct answer to this question is possible with the mention that the general setting (southern placement, low elevation, sheltering mountains and some distance from the sea) is the main cause and the smaller scale topography (surrounding steep slopes) is much less relevant.
While far less impressive as in the case of a “cold trap” (known as frost hollow), where the simple law of gravity can create huge differences between the bottom and rim of a small closed basin, I think that a hypothetical “heat trap” with measurable enhancing properties could be possible with some specific topography, but due to the simple fact that the warmer air has the tendency to rise, not to sink as the colder one, it’s certainly much more difficult to “balance the ingredients” in the proper way to attain it. Maybe a future project.
