Cowles Bog Trail
The wetlands-to-dunes route offers a spring hike, but deep sand and steep dune climbs make it more demanding than a flat marsh walk.
May · Cowles Bog Trail
What to see and do in Indiana Dunes in May
Choose a May outing that fits the route, weather and effort involved.
Great Marsh birding
Choose wetland birding during spring migration; no fixed peak week follows from the park’s general migration guidance.
May · Great Marsh birding
Indiana Dunes weather in May
May’s normal high is 71°F and low is 49°F, with 4.59 inches of precipitation. Valparaiso Water Works at about 800 ft is an inland proxy south of the park, not a beach station. Lake breezes, waves and lake-effect snow can make shoreline conditions different. Air temperatures do not establish swimming conditions.
Cooler Hotter
Jan
High32°F
Low18°F
Precip · in2.38
Feb
High36°F
Low21°F
Precip · in2.24
Mar
High48°F
Low29°F
Precip · in2.63
Apr
High61°F
Low39°F
Precip · in3.74
May
High71°F
Low49°F
Precip · in4.59
Jun
High80°F
Low59°F
Precip · in4.33
Jul
High83°F
Low63°F
Precip · in4.10
Aug
High81°F
Low62°F
Precip · in3.57
Sep
High75°F
Low54°F
Precip · in2.92
Oct
High64°F
Low44°F
Precip · in3.93
Nov
High49°F
Low34°F
Precip · in3.26
Dec
High37°F
Low24°F
Precip · in2.58
Indiana Dunes crowds in May
May averages 291,748 recreation visits, 57% of the peak monthly average in July.
LowestLowModerateHighPeakAverage month: 235,200May
Tips for your May visit
Check the approach before choosing the rest of the day.
AWest Access (Paul H. Douglas Center)BCentral Access (Indiana Dunes Visitor Center)CEast Access (Mount Baldy)
- Park boundary
West Access (Paul H. Douglas Center)
Normal road approach, subject to weather and individual site restrictions.
How we built this page.
An independent guide using official data. Not affiliated with or endorsed by the National Park Service.
- Crowds
- 2021–2025 monthly averages. NPS recreation visits, compared with the park’s own busiest month. Visits are not unique visitors or a count of people on a trail.
- Weather
- 1991-2020 climate normals. NOAA’s Valparaiso Water Works, IN station. These describe typical weather at the station, not every part of the park or a forecast.
- Roads & lodging
- Normal seasonal schedules. NPS guidance and official operator information. Confirm access, hours and availability before you travel.
Historical records and data-quality checks
- Visit history: 1979–2025 NPS monthly recreation visits.
- Weather history: 1893–2025 daily observations, separate from climate normals. We average daily highs and lows and total the rain for each month.
- Complete months only: every day must pass our quality checks for that metric. Missing or incomplete records stay blank; we never interpolate.
- Excluded measurements: flagged, presumed-zero and lagged values. Trace rain counts as zero measurable rainfall.