summer' written all over it. Markku Salo recorded "On lämmin" (It is warm) in 1965. I'm afraid I don't know anything about Markku Salo. He recorded three unsuccesful singles in 1964-65 and was never heard of since. Which is kind of pity, becouse at least this song shows that he would have got some potential. The original summer song was called "In Summer" and it was performed by Billy Fury, (b. Ronald William Wycherley). Billy was a successful British singer from the late 50's to the mid 60's. Fury's Elvis Presley -influenced, hip-swivelling, and at times highly suggestive stage act contributed to his popularity. He never had number one UK hit, but this "In Summer" reached as high as number 5 in 1963.
Here's the pair: