Unusually warm July ends with heavy thunderstorms

According to the Finnish Meteorological Institute, the average temperature for July varied between the nearly 20 degrees Celsius in southern and central areas to about 15 degrees in northernmost Finnish Lapland. All of Finland was warmer than usual. The greatest deviation was in the northwest arm of Enontekiö, where the average temperature was more than four degrees higher than usual. The smallest deviation was in the southern and eastern parts of Finland and in the Inari area of Lapland, where the temperature was about two degrees above normal.

In Western areas July was generally unusually warm, with temperatures reaching levels that are reached on average once every ten years. In Lapland the average temperature is generally exceptionally high, reaching levels that are recorded on average once every 30 years in July. Most recently, Lapland had a July that was about as warm as this year in 2003. In southern and central areas, the warmest July ever recorded was in 2010. 

Temperatures exceeded 25 degrees almost every day

The highest temperature i the month, 32.5 degrees, was measured in Utti in Kouvola on the 26th of the month. Temperatures exceeding 25 degrees were recorded on 26 days of the month, while the average for July is 16 days.  Since 1959, the number of days in July in which the temperature exceeded 25 degrees was greater than this year only in 2010 and 1973, when they numbered 30. In 2003 there were 28 and in 1972 there were 27.  The number of days with temperatures exceeding 25 degrees was greatest at the Utti weather station in Kouvola, where they numbered 22.

There were great local differences in rainfall in the month, because most of the rain was in the form of showers. Generally speaking it rained less than usual.  Only in parts of Eastern Finland, Ostrobothnia, and Finnish Lapland did the total amount of rain exceed the average levels. It was driest in southwestern areas and in northernmost Finnish Lapland, where rainfall was less than 30 millimetres, which is well below half of the long-term average. In central and northern parts of Finland, rainfall exceeded 80 millimetres in some localities.  Of all of the observation stations, rain was heaviest in Kuja-Kokko in Kauhajoki, where it rained 147.1 millimetres. The least amount of rain, 10.6 mm. was recorded in Kumpula in Helsinki The greatest amount of rain in a 24-hour period, 62.3 mm. was recorded in Pellonpää in Oulu on the 18th of the month. 59.2 millimetres of the rain came down within the period of one hour.

Number of lightning strikes nearly twice the average

In July a significant number of cloud to ground lightning strikes were pinpointed. In a month nearly 110,000 cloud-to-ground lightning strikes were observed, while the long-term average for July is about 59,000 lightning strikes. Lightning activity was especially heavy in May as well.  So far this summer nearly 150,000 cloud to ground lightning strikes have been pinpointed, while the average number for an entire summer is about 138,000. Statistically, about 30,000 lightning strikes are expected in August.

July concluded in a brisk day of lightning; on the last day of the month about 22,000 lightning strikes were observed. This is a statistically significant, but not a record-breaking number of lightning strikes in a 24-hour period. The largest number observed in one day in the 21st century, 28,500 lightning strikes, occurred last summer on June 26.

The last thunderstorms of the month were also significant in their frequency of lightning strikes. At Taivalkoski 81 cloud to ground lightning strikes were observed over an area of 100 square kilometres. A thunderstorm is seen to be exceptionally heavy if the number of strikes exceeds 80 per 100 km2 in a single day. Similar densities do not occur every year. Thursday's heavy thunderstorms are the sum of many factors, but for instance, the amount of moisture in the lower atmosphere were exceptionally great.  Strong gusts of wind occurred in connection with thundershowers especially in central parts of the country and in Kainuu, causing damage to forests and electricity blackouts.

Further information:

Thunder and lightning: Peter Ukkonen, Tel. +358 50 452 9104, peter.ukkonen@fmi.fi

Weather statistics: http://ilmatieteenlaitos.fi/kuukausitilastot (in finnish)

Thematic information on heavy storms:http://ilmatieteenlaitos.fi/rajuilmat (in finnish)