Localized electromagnetic focused heating from a finite rectangular aperture antenna array into a lossy medium is considered in a quantitative manner. The general prescription for focusing the electric field components is given. In particular, two types of focusing are presented that have applications in hyperthermic cancer therapy and geophysical sub-surface probing. It is shown that, for low loss tangents, the focusing can be very sharp but it deteriorates significantly for higher loss (e.g., for loss tangents greater than 0.20).