In summer the mean daily temperature is consistently above 10°C. Summer usually begins in late May in southern Finland and lasts until mid-September.
The regions north of the Arctic Circle are characterized by “polar days”, when the sun does not set at all. The northernmost parts of Finland have 73 such days every year. Even in southern Finland, the longest day (around Midsummer) is nearly 19 hours long. The warmest day of the year comes about one month Midsummer, i.e. around July 20, in the whole of Finland.
The highest summer temperatures in the Finnish interior are from 32°C to 35°C. Near the sea and over the maritime islands, temperatures over 30°C are extremely rare; the highest temperature ever recorded in Helsinki is 31.6°C.
To conclude, the weather at the beginning of June can be unpredictable. It can be sunny and fairly warm but if unlucky it could be cool and rainy. Please pack some practical clothing with you and prepare for cool nights.
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