spring weather covid-19

It's now just over 12 months since the COVID-19 pandemic impacted our lives, with countries and their economies going into lockdown to prevent the continuing transmission of what was a very unknown, and serious virus that was making people very ill and overwhelming healthcare systems.

Now as we approach Spring 2021, we know a lot more about the virus, introduced better treatments to help those infected with COVID-19 and now a growing number of nations are rolling out mass vaccination programs, which will hopefully help the world build a level of immunity. 

It’s fair to say that an incredible amount of progress has been made in the world's response, but it can be hard for people to share the positive outlook with most of Europe still in lockdown. However, the increase in daylight and temperatures over large areas of Europe last weekend, not only dispelled some of the winter gloom, but actually helped lower the amount of virus prevalent in the population. 

Last year early evidence emerged that the virus is impacted by UV, temperature and relative humidity, with a scientific paper published on “Airbourne SARS-COV-2 Is Rapidly Inactivated by Simulated Sunlight” in The Journal of Infectious Diseases (2020). Meteomatics AG has utilized the findings to create a predictive model to estimate virus decay, which can provide an estimation of COVID-19 half -life anywhere on the globe.

The half-life of COVID-19 determines the time until 50 % of the virus dies outdoors. Investigations have shown that the half-life time strongly depends on temperature and humidity. The decay of the virus is also affected by sunlight, which causes instability of COVID-19 viruses in aerosols. The half-life of COVID-19 is available in the Meteomatics API Health Parameters.

The impact of sunlight, temperature and humidity has led to theories that the prevalence of COVID-19 could be seasonal, with less of the virus around in the environment and thereby reducing transmission in summer. During wintertime the received solar radiation on the earth’s surface is at its minimum in the higher and mid latitudes. The combination of cold temperatures and low radiation levels favour the survival of COVID-19 viruses. This is the reason why decay rates of the virus tend to decrease during winter. The figure below shows the global distribution of half-life times (top) and air temperatures (bottom) during the cold outbreaks in mid-February in Europe and North America. 

COVID-19 half life times (top) & air temperature (bottom) in mid-Feb 2021

COVID-19 half life times (top) & air temperature (bottom) in mid-Feb 2021
















Extremely cold temperatures caused the half-life times of the virus to increase significantly. Looking at South America reveals the positive effects of warm or hot temperatures combined with high humidity levels during summertime. Even at night without any solar radiation, the half-life times are much shorter compared to those on the northern hemisphere. The positive impact of solar radiation is shown by the blue area over Africa and India. Half-lifes shorten rapidly between sunrise and sunset. In mid-February this effect is also observed in the higher latitudes, since the elevation of the sun has already noticeably increased as we approach the Equinox in March.

The chart below shows a comparison of the global radiation received on earth at noon at the end of February (left) and on the Winter Solstice in December (right).

Comparison global radiation at noon in late Feb & December

Comparison global radiation at noon in late Feb & December













The difference can be clearly seen looking at Scandinavia, where hardly any solar radiation reaches the northern parts in December. In February the irradiated regions have clearly extended towards the north and the solar radiation has increased in the mid latitudes.

By the end of February, spring weather spread across wide parts of Central Europe. The mild temperatures combined with increased solar radiation have a very positive impact on the decay rate of the COVID-19 virus during daytime. At night the half-life's elongate once again as the minimum temperatures are still quite cool.

Mild temperatures combined with increased solar radiation have a positive influence on the virus

Mild temperatures combined with increased solar radiation have a positive influence on the virus.


















Although, areas of extremely low humidity, like the Australian Outback or the Sahara desert, show quite long half-life's during night-time compared to adjacent regions with higher humidities, as illustrated in the chart below.

Areas with high humidity show long COVID-19 half lives

Areas with low humidity show longer COVID-19 half lives.
















The reduction of COVID-19 half-life due to increased daylight and warmer weather, give hope that many of us can now start looking forward to the end of this tough winter!

As the more favourable weather conditions reduce the amount of virus in circulation, helping reduce infection rates at the best possible time, with many governments accelerating their vaccination programs. The combination of a decline in the infection rate and numbers of people vaccinated could help the world begin its recovery from the health, social and economic impacts this awful pandemic has brought to us all.

Meteomatics AG is a private weather business, making a rich database of weather information and insights available to users across the globe, offering incredible detailed forecasts: downscaled to 90 meters and up to 5 minute temporal resolution. Through an easy to use RESTful API endpoint. Please contact [email protected] if you would like any further information on our COVID-19 half-life parameter or interested in obtaining an account.