I would like to use SUMIF to add up numbers occurring in a row that spans 12
columns (months of the year) if the condition is met in the same row in
another column.

This is how I tried it: =SUMIF(B2:B13, "=STA", H2:S13)

The conditon STA can appear in several rows in the range in column B.

It works perfectly if there is only one column in the sum_range, but not
with more than one.

Can this be done?