HOBO ProV2 is logger which we use in the department for recording ambient temperatures continuously

Dear Masha

I recommend that you read this article, it is simple but it presents a method to estimate soil temperature based on air temperature.

Soil temperature estimation at different depths, using remotelysensed

data. Journal of Integrative Agriculture 2020, 19(1): 277–290.

Also, check this web page, here is data on soil temperature and air temperature for everyone, they could be useful to you.

https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-land?tab=overview

I hope this information is useful for you.