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Climate change, which was particularly marked at the turn of the 20th and 21st centuries, was accompanied by unfavourable weather phenomena. One of whose effects cannot be prevented is hurricane. Much of the most devastating storms (e.g. Kyrill in January 2007, Carmen in November 2010), which crossed over Poland, was associated with low pressure systems. The occurrence of high wind speeds in the cold season is a natural feature of Polish climate. Hurricanes in the summer are generally characterized by more complicated origin. The cause of the damage at this time of year may be squall fronts and tornados (e.g. July 4th, 2002 – Puszcza Piska; July 20th, 2007 – Częstochowa region). An important issue is to develop a category of winds for the forest district, which can have destructive effect on the stands. Current research shows that gusty winds exceeding 11 m/s may cause first damage to the trees, while blows with velocity exceeding 30 m/s result in severe damage. Knowing and monitoring the mechanisms that leads to strong winds, assessing their impact, and managing risk in the context of their effects is one of the important elements of a forest management strategy. On August 11th, 2017, after the influx of hot tropic air, much cooler polar air began to flow from the west. In the afternoon and evening storm cell and supercell began to form in the south−west of the country. Later on, they moved in the north direction forming a squall line. With a Mesoscale Convective System (MCS) moving to the north, there was a gusty wind exceeding 40 m/s in some places. A gust of wind occurred around 18.30 (EET) in Dolny Śląsk (SW Poland) and after about 2 hours in Pomerania (N Poland). The pressure tendency during the transition reached 4−5 hPa. In the northern part of the country, gusts of wind were the largest and occurred several times in 2−3 hours. The system was accompanied by heavy precipitations, which in north Poland determine more than 60% of the average monthly rainfall. The effect of moving MCS was the damage of almost 80 thousand hectares of forests in Poland, which of more than 39 thousand hectares were classified to complete restoration.
On July 8, 2010 and 9 VII 2011 in Przybrodzin by Lake Powidzkie (UTM: XU91; 52°25’45” N, 17°55’47” E) a male and a female of Onychogomphus forcipatus were recoded respectively. More than 30 years ago on nearby Lake Niedzięgiel and Białe, situated at the same UTM square UTM (XU91), the presence of the species was found. All of the discussed lakes are located at the distance more than 100–130 km towards the west, north-west and north of the nearest known sites of the species (Bernard i in. 2009). Probably the sites from the Gnieźnieńskie Lakeland are disjunctive area of the occurrence of the species, however, the existence of other sites joining them with more densely inhabited area of lake districts can not be excluded. Duration of the distribution island in the Gnieźnieńskie Lakeland confirms the maintenance of the suitable habitat base, especially lakes with good water quality.
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On the basis of term values (12 UTC) of meteorological data of seven synoptic stations in the central-west Poland heat stress index (HSI - Heat Stress Index) was calculated. During the year the heat stress of varying intensity occurred from February to November with a maximum in August. The rest of the year was dominated by thermoneutral conditions. In the period 1971-2006, and especially since 1999, becoming more frequent of occurrence days with an intensity of heat stress was so great, that pose a risk increase in body temperature (HSI > 100%). Based on the frequency of the occurrence of days with values HSI > 30% in the central-west Polad three areas with different number of days chargeable was distinguished.
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