When Mother Nature is generous with rainfall

It is usually easier to add moisture,  than take it away.  

We have received reports of high rainfall in areas of the country that has caused caused concern for gardeners.  There have been yellow leaves on lower portion of lily stems that fall off, smaller flowers this year and even "no-shows" in some cases.  If even your established lilies are showing any of these symptoms, it is a good idea to check the moisture content of your garden now.  Additions of moisture-retentive peat, manure or compost around the bulb when planting tends to keep the soil wetter than lilies are able to use.  If you are seeing yellow leaves, cut back on summertime watering.  

If Mother Nature has dropped abundant water too often on your garden, remove any mulch surrounding the lilies to allow the soil to dry faster as a quick fix.   Only water when your soil is dry one inch or two below the surface, and then leave the water on long enough, so the ground is moist 6 to 8 inches deep.  Your shrubs and trees will also appreciate the deep watering, which will help them to tolerate periods of drought.

Correct questionable drainage by making a raised bed.
Clay soil with sluggish percolation is a reality for many gardeners on flat terrain. Provided your garden is not covered by stagnant water for extended periods of time, abundant rainfall with good drainage allows oxygen-filled water to wash over the roots. Lilies can tolerate a lot of moisture for a short time. By slightly raising the planting area so that the bulbs themselves are above ground level, their roots may still penetrate into waterlogged soil and the survival of your choice cultivars will be ensured. The basal plates (bottom) of larger bulbs may be 8 to 10 inches below the surface; therefore your raised area should be about 12 inches high for best results.  

Choose a sunny site for your new lily bed this summer. It is not necessary to lift turf, but persistent roots of bindweed, thistle or other difficult to eradicate weeds require removal. Outline the area with landscape timbers or used railroad ties, pounding 12 to 18 inch long sections of pipe or "rebar" into the ground to steady the wood, and back fill with fresh topsoil, amended as mentioned earlier. To keep moles, voles, gophers and other tunneling varmints out of the bed, lay down 1/4" galvanized wire cloth from the hardware store before setting your landscape timbers on top, bringing the wire up around the outside of the wood. Using "horseshoe nails" or heavy wire staples used on fences, attach the woven wire to the outside of the timbers, using soil or creeping plants to soften the edges and hide the barrier.

Although coarse sand can be added for additional drainage, Perlite is a better choice for a lighter mixture. If moles, voles or gophers are abundant in your area, place a barrier of 1/2 inch galvanized hardware cloth on top of the ground, installing your timbers on each end. If your new bed is wider than the barrier screen, overlap the wire by one or two inches. On large raised beds, mound soil higher in the center, sloping down to one inch below the height of the timbers on the edge. If desired, plant short-growing Hemerocallis with daffodil bulbs in the outer 12 inches for a unified border. These smaller daylilies will hide the decaying foliage of the spring bulbs, plus soften the appearance of the timbers with color and green foliage throughout the summer and fall. For newly constructed beds in late summer, wait at least one year before planting new lily bulbs in fall if you are in a more severe climate, to allow the soil to settle. In an emergency, you can use a thick layer of mulch (12 inches of straw, etc.) over the beds for winter in colder climates - removing it during spring thaw -  to help insulate the lilies before the soil has compacted enough.  In milder climates, Zone 7 and higher, no mulch over winter is necessary.