What to look for in nature in Illinois this May

Are piping plovers nesting on Chicago's Montrose Beach in May?

• The nesting calendar

  Courtship and nest scrapes from mid-to-late April; eggs hatch from late May to early June; chicks fledge 25 to 35 days after hatching · Sandy Great Lakes beaches, including the Montrose Beach Dunes in Chicago

  According to federal wildlife biologists, plovers reach their breeding grounds in early April, begin courting and nesting in mid-to-late April, and share incubation duty for 25 to 28 days. Add those numbers together and a nest started in late April hatches around the last week of May or the first week of June, then the downy chicks run and feed on their own for a month or so before they can fly. The Great Lakes population was listed as endangered on December 11, 1985.

• What Chicago has seen so far

  Past years vary from one fledged chick to none · Montrose Beach and its fenced dunes

  The Chicago Piping Plovers partnership keeps a year-by-year record. Chicago's first nest in decades produced two fledged chicks in 2019, followed by three in 2020 and two in 2021. In 2022 one of the adults did not return from Florida and the other, Monty, died on May 13. No nesting was reported in 2022 or 2023, and in 2024 a new pair fledged one chick. The partnership's site is the place to find out which birds, if any, are on the beach in 2027.

• Sharing the beach

  Whenever birds are present, from April into July · Chicago's fenced dunes and other Lake Michigan nesting beaches

  The partnership asks only that people give the plovers the space they need to nest and raise chicks. In practice that means staying outside the posted enclosure, keeping dogs far away, taking photos with a long lens, and never walking toward a bird that runs or fakes an injury. A chick no bigger than a cotton ball can vanish into a footprint.

When is warbler migration at its peak in Illinois, and where should you look?

• Montrose Point and the Magic Hedge

  May, especially the mornings after overnight flights · Montrose Point Bird Sanctuary, Lincoln Park, Chicago

  The sanctuary juts into Lake Michigan, and migrants that have crossed or followed the shore drop into its thickets to feed. The Chicago Park District counts over 300 bird species at the sanctuary and the adjoining dunes. Its best-known patch is the Magic Hedge, a roughly 150-yard stretch of shrubs where the Army planted honeysuckle to screen its barracks. The barracks are gone and the birds still use the cover. Walk slowly, look low as well as high, and keep to the paths.

• Read the migration before you go

  BirdCast's migration tools run March 1 to June 15 · Online, with live and forecast maps

  Cornell Lab's BirdCast offers forecast maps that show how much migration to expect and when, and live maps that show it in progress, with arrows for flight direction. BirdCast adds that over four in five North American migratory species fly by night, which is why a heavy flight overhead can mean a hedge full of warblers the next morning, even in a city park.

• World Migratory Bird Day

  Held in May each year; the 2026 date was May 9 · Local bird walks and counts nationwide

  The organizers' site gave May 9 and October 10 for 2026 and showed no 2027 date yet. Expect a May date, and look for walks from the Illinois Audubon Society, forest preserve districts and Chicago-area bird groups, whose May programs are typically announced in spring. Check each organizer's page for time and place.

• Lights out for night migrants

  Spring and fall migration · Cities and towns across Illinois

  BirdCast reminds readers that artificial light and glass are dangerous to birds flying at night. Chicago Bird Alliance has long pushed for a bird-friendly building ordinance and says it needs more City Council support. At home, turning off decorative outdoor lights and closing blinds at night costs nothing.

Which summer birds arrive and start nesting in Illinois in May?

• Scarlet tanagers

  Arrive in late April; breeding runs May through August · Upland and bottomland forests, mainly across the northern part of Illinois

  IDNR says the female builds her nest on a horizontal branch, often in an oak or hickory, anywhere from 8 to 75 feet up, and lays three to five green-blue eggs that she incubates for 13 to 14 days. You will hear the male first: his song resembles a robin's, with a burrier edge, and his call is a chip-burr. Look in the high leaves of mature woods.

• Indigo buntings

  Males arrive before females in April; breeding from May to mid-August · Edges of bottomland forest, shrub prairie, old fields and roadsides

  The male sings through the day with paired notes, often written as sweet-sweet. The female builds a cup nest low in dense vegetation, may weave in a piece of shed snakeskin, lays three or four pale-blue eggs and incubates them alone for 12 to 13 days. IDNR notes that pairs can raise two broods in a year and that cowbirds sometimes lay in their nests.

• Common nighthawks

  Return from April; the nesting season runs May through July · Open ground and flat gravel rooftops in towns and cities

  IDNR lists the nighthawk as a common migrant and summer resident, and says it builds no nest: the female lays two eggs on bare ground or a flat roof and incubates them alone for 19 days. Look up at dusk for slim, long-winged birds with white wing patches, flapping erratically over streetlights and ball fields.

What lives in Illinois wetlands and swamps in May, from pelicans to bullfrogs?

• Shorebirds, pelicans and ibis on the Illinois River

  May is one of the two best shorebird months; ibis late May to early June · Chautauqua National Wildlife Refuge near Havana; Emiquon Preserve near Lewistown

  The refuge says May and August can be the best times to see many shorebird species, especially sandpipers, with gulls and terns, and that commotions of American coots arrive in late spring. Late May to early June, ibis may be spotted. American white pelicans, which IDNR calls a migrant through most of Illinois, often dominate the landscape there in summer. Check refuge water levels before driving: mudflats come and go with the river.

• Cypress swamps and prothonotary warblers

  Warblers return from April; nesting May through June · Cache River wetlands in Pulaski and Johnson counties, including Cypress Creek National Wildlife Refuge

  IDNR calls the prothonotary warbler a common migrant and summer resident of southern Illinois, living in swamps and bottomland forests and nesting in tree holes, nest boxes or under bridges, with clutches of three to eight eggs. The Cypress Creek refuge says bald cypress and water tupelo grow along its waterways, that canoeing is the best way to see the swamps, and that summer visitors may find many songbirds, including prothonotary warblers. Indiana bats, an endangered species, use the refuge as well.

• Snake Road reopens to foot traffic

  Closed to vehicles March 15 through May 15 in the Forest Service’s 2025 notice; confirm the 2027 dates · Shawnee National Forest, LaRue-Pine Hills area, on Road 345

  The Forest Service closes the road each spring and fall so that snakes and amphibians can cross between limestone bluffs and LaRue Swamp. The Forest Service’s March 2025 notice gives March 15 through May 15 for the spring closure, and we did not find a 2027 notice, so confirm the dates with the forest. In that notice the road is closed to vehicles but open to people on foot. The Forest Service says collecting or handling these animals is prohibited, and some are threatened or endangered, so look and photograph only.

• American bullfrogs

  Breeding runs late April through August · Lakes, rivers, marshes, ponds and creeks statewide

  IDNR describes the bullfrog's call as a jug-o-rum, with males defending territory against rivals. A female lays about 20,000 eggs in water, the eggs hatch in under a week, and tadpoles take about 14 months to transform, growing to more than six inches. A big green tadpole in a pond in May is likely last year's.

• Fireflies

  Adults begin flashing as spring turns to summer; Xerces gives no Illinois date · Edges of ponds, wet meadows and woods

  The Xerces Society says about one in three assessed North American firefly species may be at risk of extinction, citing habitat loss, light pollution, pesticides, climate change and poor water quality. Its advice: turn off outdoor lights at night, protect and restore good habitat, and join community-science projects that track where fireflies occur. Note the date of your first flash and send it to a tracking project.

Which woodland wildflowers bloom in Illinois in May?

• Early May woodland peak

  Early May, the climax of the show · Allerton Park near Monticello and similar rich woods

  The naturalist names Solomon's seal, Jack-in-the-pulpit and blue-eyed Mary among the species in flower and says Virginia bluebells are still carpeting bottomland forests in May. Jack-in-the-pulpit has a hooded flower on a short stalk, easy to miss until you crouch.

• What blooms at The Morton Arboretum in May

  Mid-May, according to the 2026 weekly reports · The Morton Arboretum, Lisle, DuPage County

  The arboretum's final 2026 bloom report, on May 13, listed Korean lilacs near the Visitor Center, buckeyes, black locusts in full white bloom, blue woodland phlox and pink wild geranium lingering in woods and glades, and great white trillium on the south side of Lake Marmo. The May 6 report added pawpaw trees with dark maroon flowers and American bladdernut. The 2027 reports have not been posted; the arboretum usually publishes them on Wednesdays through spring.

• When the first prairie flowers open

  Late May through August · Nachusa Grasslands, Markham Shkode Prairies and Midewin National Tallgrass Prairie

  The Nature Conservancy says the state's showy prairie wildflowers thrive from late May through August, naming purple coneflower, wild lupine and bergamot. That means the bloom is only beginning in the last days of May.

Can you still see bison calves and prairie birds in May?

• Bison calves at Nachusa

  Calves are born April through June · Nachusa Grasslands near Dixon, Lee and Ogle counties

  Friends of Nachusa say newborns weigh about 50 pounds and wear a rusty-orange coat. They keep up with the herd within hours, nurse for about seven months and are weaned at about a year. The Nature Conservancy puts the herd at about 100 animals roaming roughly 1,500 acres. The Friends advise staying at least 100 feet back, using the pull-offs, and never entering the unit on foot. Cows are fiercely protective of calves.

• Grassland birds at Midewin

  Late spring and early summer · Midewin National Tallgrass Prairie near Wilmington

  The Forest Service lists upland sandpipers, dickcissels, bobolinks, grasshopper sparrows and Henslow's sparrows among the nesters, with loggerhead shrikes in shrubby trees along the edges. Staff monitor grass height in late spring and early summer, because short, grazed grass suits some species and tall grass suits others. Owls and harriers hunt voles in the southeast bison pasture late in the afternoon and in the early evening.

• Prairie-chickens at Prairie Ridge

  Booming season runs into early June · Jasper and Marion counties, at the Prairie Ridge natural area

  IDNR's 2022 account describes the booming season as running from April through early June. Dawn is the time. Stay in your vehicle or at the viewing area and never walk onto a booming ground.

What is May weather like in Illinois, and when do tornadoes peak?

• Tornadoes and hail

  Tornadoes are most frequent in May and June; hail peaks in May and June · Northern Illinois, per the Chicago forecast office; the whole state is exposed

  The National Weather Service in Chicago says tornadoes are most frequent in May and June, and damaging hail peaks in May and June, averaging two to three days per month with at least one report in 2005–2024. Damaging wind peaks later, in June and July. Its tornado-report average for the past decade is 26 per year, against 19 for 2005–2024 and 11 for 1950–2024, a difference that reflects better reporting as well as weather.

• Flash flooding

  May rain, especially on saturated ground · Creeks and low roads statewide

  Rain is heaviest in the south, with 5.18 inches normal at Carbondale and 5.93 at Anna. Turn around when water covers a road, and keep clear of swollen streams below bluffs and waterfalls.

When is the last spring freeze in Illinois?

How much daylight does Illinois gain in May?

What can you see in the Illinois night sky in May 2027?

• Eta Aquariid meteors without moonlight

  Active from late April; the best mornings are around May 5 to 7 · Face east to southeast in the final hours of darkness

  The Moon is new on May 6, which leaves the sky unspoiled for meteor watching. SeaSky calls the Eta Aquariids an above-average shower, able to produce up to 60 meteors an hour at the peak, with Northern Hemisphere rates nearer 30. Illinois is at the northern edge of the good viewing, because Aquarius, where the meteors seem to originate, clears the horizon late, so plan on roughly ten to thirty meteors an hour from a country site, and fewer in the north.

• The Flower Moon and a seasonal Blue Moon

  Exactly full at 5:59 a.m. CDT on Thursday, May 20, so watch the rise on Wednesday evening, May 19 · Chicago moonrise is about 7:54 p.m. that evening, low in the east-southeast

  The Moon is full in the dawn hours of May 20, so the evening before is the one to watch it rise. Four full moons fall between the March equinox and the June solstice, and SeaSky counts this one as number three, so under the older seasonal definition it earns the Blue Moon label. By the calendar-month rule there is no Blue Moon in 2027. It still looks like any full moon.

• Mercury in the evening

  Good views from mid-May into early June, with greatest eastern elongation on May 28 · Low over the western horizon roughly an hour after sunset

  SeaSky lists the greatest eastern elongation on May 28, at 22.9 degrees from the Sun. Our own figures for the Midwest have Mercury setting about an hour and a half after the Sun in mid-May, which would make this the best evening view of the year. Find a flat horizon and use binoculars if needed.

• Jupiter, Mars and a quarter moon

  May 12 and 13 · High in the south-southwest in the evening

  Our own figures put the first-quarter Moon close beside Jupiter in the evening of May 12, and a few degrees from Mars the next day. Both planets stay in the evening sky all month.

• Venus and Saturn before dawn

  Closest on the morning of May 7, near each other May 6 to 8 · Just above the eastern horizon in early dawn

  In our own figures, Venus and Saturn pass within about 0.6 degrees on May 7 and within a degree on the mornings either side, yet both hug the horizon. Treat it as a challenge for binoculars and an open view east.

• Milky Way mornings

  Moonless pre-dawn windows: the first two weeks of May and again May 25 to 31 · Low in the southern sky before dawn, far from city glow

  From a latitude near 40 degrees, our calculations give up to roughly three and a half hours of moonless pre-dawn darkness with the galactic center up, at the beginning and end of the month. A dark site far from Chicago helps.

What can Illinois families do outside in May?

Safety notes for May in Illinois