Hail, Downpours and the Omaha Driveway

How much rain arrives, and how fast

Eppley Airfield's 1991-2020 normals put 30.62 inches of precipitation in an average year, and more than a third of it, 11.83 inches, falls in June, July and August. May is the single wettest month at 4.76 inches. The totals matter less than the delivery. The station averages 19.1 days a year with half an inch or more and 7.2 days with an inch or more, and the heavy days cluster in the warm months: 1.2 in May, 1.0 each in June and July, and 1.2 in August.

The city plans its drainage around the same pattern. The Omaha Regional Stormwater Design Manual, working from a National Weather Service rainfall atlas, sizes local systems for 3.0 inches in 24 hours as the two-year storm, 4.6 inches as the 10-year storm and 6.7 inches as the 100-year storm. A two-year storm has about even odds of arriving in any given year, and a driveway expected to last two or three decades should expect to see a couple of the 10-year kind.

What the records say about hail

Nebraska earns its hail reputation. The Insurance Information Institute counted 315 major hail events in the state in 2025, meaning stones an inch across or larger, fourth among the states. NOAA's National Severe Storms Laboratory places the country's hail maximum where Nebraska, Colorado and Wyoming meet, an area that averages seven to nine hail days a year. Omaha sits at the opposite end of the state from that corner, but the statewide count shows how often hail-producing storms cross Nebraska.

Hail forms when thunderstorm updrafts carry raindrops high into air cold enough to freeze them. Typical severe hail of one to one and three-quarter inches falls at 25 to 40 miles per hour, according to the laboratory, and it is known for damaging homes, cars and aircraft. Summer in Omaha brings relatively frequent thunderstorms, and the warm months from May through August deliver most of the inch-plus rain days above.

For a driveway, the documented risk in a hailstorm is the water that comes with it. None of the public records behind this site measure hail damage to asphalt pavement, and the hail damage the severe storms laboratory lists is to homes, cars and aircraft. What storms reliably do is move a large volume of water across and around the pavement in a short time, and on loess that water is what does the damage.

Where storm water goes on a loess lot

The stormwater manual assigns driveways, roofs and paved parking lots a runoff curve number of 98, which is as close to waterproof as its method goes. Nearly everything that lands on a driveway runs off it, and the question is where. The same manual describes the soils within the city as predominantly the Monona-Ida association, deep loess that drains well once water soaks in but erodes readily where water runs across it. These are the places a storm finds first:

• Sloped edges, where runoff running along the side of the asphalt carries silt away until the edge is unsupported
• Downspouts that empty onto or beside the driveway, concentrating a roof's worth of water on one spot
• Open cracks, which SealMaster describes as the path by which water erodes base material until potholes form
• Low spots and the joint at the garage slab, where ponded water finds the nearest opening

Why loess makes small paths matter

Loess behaves in a way that turns small leaks into big repairs. People in the Loess Hills across the river call it sugar clay because it is extremely hard when dry and loses all cohesion when wet, and the hills' cat-step terraces are what saturated loess does on a slope. Under a driveway, the silt beside an undercut edge or beneath an open crack can go from firm to soft in one wet May, and the pavement over it has nothing left to rest on.

Winter then finishes what the storms started. Silt is the classic frost-susceptible soil, so water left in the base in the fall freezes into ice lenses that lift and crack the pavement. Eppley averages 96.7 freeze-thaw days a year. A driveway edge undercut in June can show as a crack by November and a dropped edge or pothole by April, which is why storm-season inspections pay off months later.

Sealing around storm season

Sealer and thunderstorms do not mix. SealMaster's application guidance rules out sealing when rain is forecast within 24 hours, because rain can wash uncured sealer away entirely, and it keeps traffic off for at least 24 hours after the final coat. May, the wettest month, averages 7.8 days with a tenth of an inch of rain or more, while September averages 5.0. That tilts the practical season toward late summer, as the post on the sealing calendar explains.

After a big storm, the checklist is short. Walk the edges for undercutting, look for new cracks and soft spots, and clear any silt or debris that washed onto the pavement before it is tracked around. Sweep it back onto the lawn rather than into the street: storm inlets in Omaha carry runoff untreated to the Papillion Creek system and the Missouri and Elkhorn rivers, and the city's stormwater program asks residents to keep leaves, clippings and other debris out of the street and never to put anything down an inlet.

Repairs that make a driveway storm-ready

The fixes that matter before storm season keep water on top of the asphalt and moving off it. Filling cracks in spring, while air temperatures run between 45 and 65 degrees and the cracks are open, closes the paths into the base, and the crack filling page explains the materials and timing. Redirecting downspouts onto turf and building up low edges with soil and grass keep runoff from cutting along the side. Sealing every two to three years, as SealMaster recommends, keeps the surface itself shedding water.

Where a storm has already done damage, such as a pothole, a sunken edge or a patch of asphalt that flexes underfoot, sealing over it will not help, and the section needs to be cut out and rebuilt on a dry base. Independent local contractors reached through the quote form can price that work, and the home page on Omaha driveway sealing explains how requests are handled.

More from the blog

• The Omaha Sealing Season, Month by Month