Semi related, why does it seem like the forecast, current temp, and historical temp, are always 10c lower than reality in summer? Happens across a few locations

Semi related, why does it seem like the forecast, current temp, and historical temp, are always 10c lower than reality in summer? Happens across a few locations I monitor, both urban and rural. I’ll often read 41c outside, 35c in shade, but the weather says it’s currently 29c.