Using data obtained by NOAA satellites, we investigate the dependence of latitude Φ of equatorial boundary of precipitating solar protons with an energy of 2.5-16 MeV on the parameters of near-Earth space (B, B_z, V, and solar wind dynamic pressure) and the activity indices (D_st and K_p). Strong correlations are found between the boundary latitude of precipitation in a dayside sector and the D_st value, and between the same latitude in a nightside sector and the values K_p (r = 0.71) and V (r = 0.85). Regression relations of Φ and the above parameters are obtained. Intervals of the parameters favorable and unfavorable for observing the PCA midday recovery phenomenon are determined, as well as latitude ranges where the phenomenon for given parameter values may be observed. The derived relations are checked by rheometric data.