ERA5 climate data · Oshkosh
Downpours in Oshkosh are up 48% since the 1990s, and the drainage was built for the old rainfall
We counted every day with an inch or more of rain in Oshkosh from 1995 to 2024. The heavy days, the ones that overwhelm drainage and drive water against the basement wall, are climbing.
Oshkosh went from 2.8 to 4.1 heavy-rain days a year.
That is a 48% rise in the downpour days that overwhelm drainage, over three decades.
What this means if you own a home in Oshkosh
Every part of a home's water defense, the grade of the yard, the gutters and downspouts, the footing drains, and the sump pump, was sized for the rainfall of the era the house went up. In Oshkosh, that era was drier. Now the downpour days those systems have to handle come 48% more often, so the water they used to shrug off is the water that now ends up against the basement wall.
You cannot change the weather, but you can resize the defenses to today's rainfall: extend the downspouts and regrade so water runs away from the house, add or upgrade a French drain and sump pump, and seal the foundation where it is already letting water through. The homes that stay dry are the ones whose drainage matched the rain that is actually falling now.
Where this comes from
Source is ERA5 reanalysis via the Open-Meteo archive: daily precipitation for Oshkosh from 1995 to 2024. A heavy-rain day is any day with 25.4mm (1 inch) or more. We compared the average annual count in the recent half of the record against the early half. Oshkosh also averages 0.3 days a year now with 2 inches or more, the ones that do the real damage.
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Oshkosh rainfall and your home: FAQ
Is it raining harder in Oshkosh than it used to?+
Yes, in the way that matters for a home. Oshkosh now averages 4.1 days a year with an inch or more of rain, up from 2.8 in the late 1990s, a 48% increase over 1995 to 2024. It is the heavy days, the ones that overwhelm drainage, that have climbed.
Why does that matter for my basement in Oshkosh?+
The grade of the yard, the gutters and downspouts, the footing drains, and the sump pump were all sized for the rainfall of the era the house was built in. When the number of downpour days rises, that older drainage gets overwhelmed more often, and water that used to run off ends up against the basement wall.
What can I do about heavier rain in Oshkosh?+
You cannot change the weather, but you can resize the defenses: extend the downspouts and regrade so water runs away from the house, add or upgrade a French drain and sump pump, and seal the foundation where it is already letting water through. The point is to match today's rainfall, not the 1990s.