if(ftype >= DNGN_MINMOVE)
        {
            // Maybe place a raincloud
            // The rainfall area is 20 (5*5 - 4 (corners) -1 (center))
            // the expected number of clouds generated by a fixed chance per
            // tile is 20 * p = expected.
            // Say an invo of 27 gives expected 5 clouds
            int max_expected = 5;
            int expected = div_rand_round(max_expected *
                                          you.skills[SK_INVOCATIONS], 27);
            if(x_chance_in_y(expected, 20))
            {
                place_cloud(CLOUD_RAIN, *rad, 10, KC_YOU);
            }
        }