September 2023 in Estonia turned out to be one of the warmest in recorded history and also saw substantially more sunshine than average, though rainfall, too, was somewhat higher than usual, ERR's Novaator portal reports.
The nationwide average ambient temperature for September stood at 15.6 degrees celsius, 3.4 degrees higher than the highest values of recent years, posted in September 1991 and 2020 respectively, and also higher than the previous record of 15.1 degrees posted back in 1934, the Environment Agency (Keskonnaagentuur) reports (link in Estonian).
Meteorologist Taimi Paljak told ERR that September this year was in essence a continuation of summer. "It was that much higher than the average, across a whole range of categories. One could truly state that September was more of a summer month than an autumn month, and wholly comparable with August."
The average ambient temperature remained above the long-term average for almost the entire month.
By day, September 12 and September 13 brought with them a new daily maximum air temperature record at several weather stations.
The highest overall September temperature, at 26 degrees, was posted on September 12, by the Kunda weather station in Lääne-Viru County.
While just few days later, on September 18, the air temperature low dropped below one degree in many places, at only 0.5 degrees in Kuusiku, Rapla County, the sharp difference between daytime and nighttime temperature values, still observable at the time of writing in early October, remained towards the end of the month.
In the final third of September, new daily records were posted, across five separate days.
Precipitation was higher at 64.2mm than the long-term average (58mm), though there were strong regional variations here.
Whereas two of Estonia's smallest inhabited islands, Kihnu and Ruhnu, saw almost double the average rainfall for the time of year, Southern (Valga, Jõgeva) and Eastern (Jõhvi) Estonia saw not much more than half the average.
The largest single day of rainfall was posted on September 14, at the weather stations both in Kunda and on Ruhnu, where a value of 90mm was recorded.
Five September days saw significant thunderstorms, with again September 14 being the most active – 1,040 cloud-to-ground lightning strikes were recorded.
Seasonal shift: September becoming more 'summery' as March becomes more 'wintry'
In September, there was not a single day without sunshine at the monitoring stations, and the sun shone more than usual at all stations.
Throughout September there was not a single day without sunshine as recorded at the meteorological stations, and an above average sunshine duration was posted at every station.
The average sunshine duration for September stood at 196.9 hours, compared with a long-term average of 157.5 hours.
Paljak said the higher-than-average levels of precipitation came only on single days, however; most of the month was unusually sunny and therefore dry. "In recent years, meaning over the past decade, September has increasingly become a summer-like month. Meteorologists have at the same time observed that March is getting colder and snowier as September is getting warmer."
As a result, both the end of summer and the start of the following spring have been delayed. "Winter is shifting into March, and summer into September," Paljak summed up, noting that April is also tending to be cooler than was earlier the case.
The warm start to fall has been observed across Europe and is one factor behind projected lower natural gas prices for the upcoming winter.
Heating season traditionally runs from October 1 to March 31.
Editor: Andrew Whyte