Windows in Delaware deal with humidity statewide, salt on the coast, and real drafts inland when the temperature drops. Hardware near the ocean pits and sticks. Wood sash in older inland towns swells in summer and gaps in winter. A fogged insulated unit in a suburb is a third problem, and it is not fixed the same way as a rotten sill. Describe the opening you have and the direction it faces.
Older houses in the northern part of the state and in the older inland towns often still have wood units, sometimes painted tight. Beach houses may have newer units whose frames and weep holes are already chalking from salt. A milky pane can sometimes be swapped without destroying the frame. Soft wood at the sill means the wall has been taking water. Say which of those you see, and say whether the leak is through the glass or around the trim.
Wind-driven rain at the beaches finds the joint between frame and wall, especially on the ocean side. Inland, the complaint is more often a draft, a sash that will not stay up, or condensation on a bath window. Storms that rattle a coastal house can also soak the stool until the paint bubbles. If original trim matters to you, say that at the start so the repair does not treat the opening like a blank hole.
You do not need a full inventory to call. Say one room, the weather side, or the whole house. Mention a bedroom on the ocean, a stair window in an older brick house, or screens and locks that have failed if those are the actual issue. Old paint on a sash that must be disturbed belongs in the description. A house used only in season should be identified, because the windows may have been waiting in the weather.
Look at the lower rail and the stool before you call. Windows in Delaware fail from salt, from humid air, or from a winter draft, depending on which end of the state you are in. Bring the wall and the symptom. Call the number on this page.