Lahti, where it's located

The climate of Lahti is cold continental, with freezing winters and mild summers.
The city is located in southern Finland, about 90 km (55 mi) north of Helsinki. The white nights occur from May 9th to August 5th.
The average temperature of the coldest month (February) is of -7.2 °C (19 °F), that of the warmest month (July) is of 17 °C (63 °F). In January 1987, the temperature dropped to -35 °C (-31 °F), while in summer, it reached 35 °C (95 °F) in July 2010. Here are the average temperatures.
Lahti - Average temperatures
Min (°C)-10-11-7-248111051-3-8
Max (°C)-4-429162023201482-2
Min (°F)141219283946525041342718
Max (°F)252536486168736857463628

Precipitation amounts to 640 millimeters (25.2 inches) per year: so, it is at an intermediate level. It ranges from 30 mm (1.2 in) in the driest month (April) to 75 mm (3 in) in the wettest ones (July, August). Here is the average precipitation.
Lahti - Average precipitation


Best Time

The best time to visit Lahti is the summer, from June to August, since it is the mildest season. However, you must take into account some rainy days and a bit of cold at night.