June 6, 2023

News Cymru

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COVID19 Greece & The Connection to the Weather

Is COVID19 in Greece driven by the weather? Greece has had two periods of cold weather (less than 10C peak daytime temperatures), one in January and one in February, what happened to cases and deaths after these periods?

14-21 January Daily temps less than 10C

Test-to-case ratio (TCR), 7 day rolling average, started getting worse on the 22nd of January, a delay of 7 days.

Worsening stabilised on the 8th of February

A 7 day period of cold weather was followed by 14 days of deteriorating (TCRs)

12-17 February Daily temps less than 10C

On the 17th of February TCR started getting worse. A 5 day delay from colder weather to worsening TCRs

Worsening appears to have stabilised around 4th of March

A 5 day period of cold weather was followed by 16 days of worsening test-to-case numbers.

Is the weather is the driver of COVID19 in Greece?

If we assume that weather caused the increased deaths from COVID19 in Greece what are the patterns?

From the onset of cold weather we expect to see a worsening in the TCR around 5-7 days later.

(The duration of the cold seems to be a weak driver)

After the TCRs start to worsen we see that a period of worsening last 14-16 days.


I have chosen days with a peak temperature 10C or less to count as a “cold period”. The actual number is probably a grey area and will therefore effect the delay between “cold” weather and the resulting worsening in TCRs.

What does this tell us about the current spike?

We could expect the current spike to stabilise and then start to improve in next few days.

Going Further Back

Greece experienced in big spike in the TCR and deaths in November, was there any connection to the weather at this time?

I see no connection, there was no “cold” weather prior, generally peak daytime temperatures were in the high teens.


For major waves we cannot say the driver is the weather or more specifically we cannot say temperature is the driver.

For minor waves, like what we are seeing at the moment, there is grounds to believe that thetemperature is a big driver. We need to see where this current uptick in TCR and deaths goes over the next week or so but at the moment, there looks to be a connection. If there is a connection, we would expect to see the situation starting to improve over the next few days.

COVID19 Greece – Further Research

While temperatures do not appear to be a driver behind the big waves, there could be a correlation with humidity.

In a further article I will look at humidity in October and November 2020 to see if there is a connection with the big spike we saw in November and December. Could a change in humidity be the driver for the biggest waves?

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