Introduction: COVID‑19 is an infectious disease caused by SARS-CoV-2. Little is known on the impact of weather conditions on the transmission of COVID‑19.
Objectives: We aimed to assess correlations between 6 different meteorologic parameters and the transmission dynamics of the COVID‑19 pandemic in 16 administrative regions (voivodeships) of Poland.
Patients and methods: Data for analysis were obtained from epidemiologic reports of the Polish Ministry of Health. For each voivodeship, one synoptic station was selected to provide meteorologic data on daily maximum and minimum temperatures, variability of daily temperature, sunshine duration, relative humidity, and wind speed. The periods with significant weather impact were determined using multiple linear regression. Cross‑correlation function (CCF) and random forest models were used to assess correlations between meteorologic parameters and the incidence of COVID‑19 as well as the number of hospitalizations for COVID‑19.
Results: In all voivodeships, the incidence of new COVID‑19 cases correlated with relative humidity (CCF = 0.41), daily maximum temperature (CCF = -0.41), variability of daily temperature (CCF = -0.40), and sunshine duration (CCF = 0.35). For all parameters, a similar time lag of 10 to 14 days was noted. There were no significant correlations for wind speed in most voivodeships. The risk of hospitalization for COVID‑19 correlated with daily maximum temperature (CCF = -0.48; time lag, 10 days) and sunshine duration (CCF = -0.45; time lag, 10 days).
Conclusions: The delayed effects of the meteorologic factors on the incidence of COVID‑19 and the risk of hospitalization for COVID‑19 were observed. In each voivodeship, the dynamics of COVID‑19 transmission was most strongly affected by relative humidity and daily maximum temperature.