**Marek Półrolniczak, Arkadiusz M. Tomczyk \* and Leszek Kolendowicz**

Department of Climatology, Adam Mickiewicz University in Pozna ´n, Krygowskiego 10, 61-680 Pozna ´n, Poland; marekpol@amu.edu.pl (M.P.); leszko@amu.edu.pl (L.K.)

**\*** Correspondence: atomczyk@amu.edu.pl; Tel.: +48-061-829-6266

Received: 10 November 2017; Accepted: 3 January 2018; Published: 7 January 2018

**Abstract:** The aim of the study was to characterise the occurrence of hot days and heat waves in Pozna ´n in the 1966–2015 period, as well as to describe the thermal conditions in the city during selected heat waves between 2008 and 2015. The basis of the study was the daily maximum and minimum air temperature values for Pozna ´n–Ławica station from 1966–2015 and the daily values of air temperature from eight measuring points located in the city in various land types from 2008 to 2015. A hot day was defined as a day with Tmax above the 95th annual percentile (from 1966 to 2015), while a heat wave was assumed to be at least five consecutive hot days. The research study conducted shows the increase of Tmax, number of hot days and frequency of heat waves in Pozna ´n over the last 50 years. Across the area of the city (differentiation of urban area types according to Urban Atlas 2012), there was a great diversity of thermal conditions during the heat waves analysed.

**Keywords:** air temperature; hot days; heat waves; climate change; city; urban area types; Pozna ´n; Poland
