Heavy rain and unseasonably low temperatures have marred the beginning of the summer holiday period in many parts of Switzerland. Authorities issued warnings as the levels of several lakes reached a critical point. Several weeks of bad weather with violent thunderstorms and intermittently heavy rain have filled up many riverbeds and lakes, particularly in the region around the capital, Bern, as well as in southwestern Switzerland. On Monday regions in central and eastern Switzerland were also hit by heavy rain. A drop in temperatures led to snow falling in the Alps above 1,800 meters at the beginning of the week. In lower-lying areas the mercury climbed to a maximum of 11 degrees Celsius on average. Experts have forecast a major improvement for the coming weekend with temperatures reaching more than 30 degrees. In April Switzerland recorded a heat wave followed by a period with heavy local thunderstorms. A freak storm in June caused damage worth hundreds of millions of francs. Farmers are concerned that the wet weather will lead to a poor harvest and difficulties in organizing work.