Daily microclimate temperature data for 2020–2024 in northern Fennoscandia

This dataset contains daily microclimate temperature observations from a network of 347 dataloggers deployed across three study areas in northern Fennoscandia: Kilpisjärvi (KIL) in northwestern Finland, Rásttigáisá (RAS) in northern Norway, and Värriö (VAR) in northeastern Finland. The observations span five consecutive years (1.1.2020–31.12.2024). The temperature measurements were collected using TOMST TMS-4 microclimate dataloggers, using the near-surface air temperature at 15 cm height. To ensure temporally complete time series, daily values have been imputed to fill occasional gaps arising from missing or erroneous measurements (see Rantanen et al. 2026 for further details). The three study areas represent contrasting northern environments: KIL (Kilpisjärvi) consists of three mountainous sub-areas (Saana, Pikku-Malla, and Ailakkavaara) characterized by strong topographic relief and alpine–subalpine vegetation. RAS (Rásttigáisá) represents a mountainous tundra environment in northern Norway. VAR (Värriö) is located in boreal forest and forest–tundra transition zones in northeastern Finland. The dataset provides daily average temperature values for each logger site, enabling analyses of growing season timing, growing degree days, cold and warm extremes, and microclimate heterogeneity at landscape scales. Coordinates of all logger sites are included in the Finnish national TM35FIN coordinate reference system. The dataset underpins a manuscript on fine-scale growing season dynamics in northern environments (Rantanen et al., 2026), which is currently under review in Climate Dynamics.