Show the records on mean sea level pressure by zip code.
select zip_code, mean_sea_level_pressure_inches from weather group by zip_code
Now group by zip code and average over the pressure.
select zip_code, avg(mean_sea_level_pressure_inches) from weather group by zip_code
Which zip code has the lowest of those?
select zip_code from weather group by zip_code order by avg(mean_sea_level_pressure_inches) limit 1