May crowns the saguaros with their creamy night-blooming flowers — Arizona's state flower — and brings the legendary sky-island birding to its peak before the heat. In the low desert the dry foresummer arrives; in the high country, spring is just unfolding.
Week by week in May
April 30 – May 6
- The first saguaro flowers open at the cactus crowns — Arizona's creamy, night-blooming state flower.
- The sky-island canyons reach their peak — Elegant Trogon, Painted Redstart, and a dozen hummingbird species.
- The Eta Aquariid meteor shower, debris from Halley's Comet, peaks in early May before dawn from a dark southern horizon.
- In the low desert, plant only the toughest heat-lovers now — okra, black-eyed peas, and Armenian cucumbers.
May 7–13
- The saguaro bloom builds, the waxy white flowers opening in waves and pollinated by bats, doves, and bees.
- Elf Owls call from saguaro cavities at dusk and White-winged Doves feast on the saguaro nectar.
- Two-tailed and Western Tiger Swallowtails patrol watered gardens as the desert heat builds.
- Up in Prescott, the Verde Valley, and Flagstaff, the milder season is just opening for warm-season planting.
May 14–20
- The Chihuahuan grasslands of the southeast host displaying Cassin's, Botteri's, and Grasshopper Sparrows.
- Hedgehog and prickly pear cacti throw their final brilliant cups as the desert annuals dry up.
- The high country comes fully into leaf — aspens shimmer green and ponderosas push fresh candles.
- The last spring greens and peas give way to summer squash, cucumbers, and the first melons.
May 21–27
- Madera Canyon, Ramsey Canyon, and Cave Creek host their full cast of Mexican specialties at the year's birding peak.
- The high-country bloom begins on the Mogollon Rim with the first penstemons and meadow flowers.
- Watered gardens with lantana and milkweed become refuges for swallowtails as the desert dries.
- Low-desert tomatoes stop setting fruit as days top 100°F — focus on keeping established plants alive.
May 28 – June 3
- The last saguaro flowers open as barrel cacti ring their crowns with orange and yellow bloom.
- Painted Redstart, Arizona Woodpecker, and Mexican Jay are on territory in the cool sky-island canyons.
- The Summer Triangle climbs in the east as the rich star clouds of Scorpius and Sagittarius rise in the south.
- In the high country around Flagstaff, the short summer season finally gets underway after the late frosts.
Birds This Month
May is the peak of Arizona's world-famous sky-island birding. The southeastern canyons — Madera Canyon, the Huachucas, the Chiricahuas, and Cave Creek — host their full cast of Mexican specialties: the Elegant Trogon nests in the sycamores, the feeders blaze with Broad-billed, Magnificent (Rivoli's), Blue-throated Mountain-gem, Violet-crowned, and White-eared Hummingbirds, and the woodlands hold Painted Redstart, Sulphur-bellied Flycatcher, Arizona Woodpecker, Mexican Jay, and a rotating cast of rarities that draw birders from around the world.
In the desert, breeding is in full swing. Elf Owls call from saguaro cavities at dusk, Lesser Nighthawks course the evening flats, White-winged Doves feast on saguaro nectar and fruit, and the resident Cactus Wrens, Curve-billed Thrashers, and Gila Woodpeckers are feeding fledglings. Lucy's Warblers and Bell's Vireos sing from the mesquite, and the last spring migrants pass through the riparian corridors.
The Chihuahuan grasslands of the southeast host breeding Cassin's, Botteri's, and Grasshopper Sparrows, Scaled Quail, and the spectacular displaying Scott's Orioles in the yucca and ocotillo.
This month's tip: bird the sky-island canyons in the cool of early morning — the dawn hummingbird and trogon show is at its absolute peak, and it's the best month of the year to chase the Mexican specialties that make Arizona unique.
What's Blooming
May is the month of the saguaro bloom — Arizona's state flower and one of the desert's great spectacles. The giant cacti raise crowns of creamy-white, waxy blossoms that open at night and last through the next morning, opening in succession over weeks. They are pollinated by lesser long-nosed bats, white-winged doves, and bees, and the ring of flowers atop each saguaro is the floral emblem of the Sonoran Desert. The other columnar and barrel cacti bloom now too, and the prickly pear, cholla, and hedgehog cacti are still throwing brilliant magenta, yellow, and crimson cups.
The desert annuals fade as the dry heat builds, but the hardy summer flora carries on: desert marigold, globe mallow, desert senna, fairyduster, and roadside brittlebush hold their color, and ocotillo may still flame scarlet. In the high country, the spring bloom is just beginning — the first penstemons and meadow flowers open along the Mogollon Rim.
Where to look: Saguaro National Park, the Desert Botanical Garden, and almost any Sonoran bajada offer the saguaro bloom — look up at the cactus crowns in the morning. The flowers open in waves through May into June.
Garden This Month
May splits Arizona's gardeners sharply by elevation. In the low desert, the dry foresummer has arrived and the job shifts from planting to keeping things alive. Only the toughest heat-lovers — okra, black-eyed peas (cowpeas), sweet potatoes, Armenian cucumbers, melons, sunflowers, and basil — should go in now; tomatoes and peppers planted earlier will set little fruit once days top 100°F, though they often resume in fall. Water deeply and early, run 30–50% shade cloth over tender vegetables, mulch heavily, and watch for spider mites and stress in the dry heat.
Give citrus its late-spring feeding and a deep soak, and harvest summer squash, cucumbers, and the first melons before they cook. Up in the transitional country and the high mountains, by contrast, May is prime planting season — Prescott, the Verde Valley, and Flagstaff gardeners are setting out tomatoes, peppers, squash, and beans as their frost dates pass at last. The same calendar that's closing in the desert is just opening in the pines.
Zone 6b (Flagstaff and the high country): the last frost is only now passing, so plant out hardened cool-season crops and wait until late May or early June for warm-season transplants. The high country's short, cool summer is just beginning — protect young plants from late cold snaps.
Zone 7a (Prescott, Verde Valley, mid-high country): prime planting now that frost has passed — set out tomatoes, peppers, squash, beans, corn, and melons, and the milder summer here lets them thrive. This is the heart of the transitional-country planting season.
Zone 9b (Phoenix, Tucson, lower valleys): the heat has arrived — focus on keeping established crops alive. Plant only the most heat-loving summer crops now (okra, black-eyed peas, sweet potatoes, Armenian cucumbers, melons, basil), water deeply and early in the morning, run shade cloth over tender plants, and mulch heavily. Tomato and pepper fruit set stalls as days top 100°F.
What's at the Farmers Market
May markets in the low desert begin their summer transition. The last spring greens, lettuces, peas, and fava beans appear early in the month before the heat ends them, while the first summer squash, zucchini, cucumbers (including the curling Armenian cucumber), green beans, and early melons arrive. Fresh herbs — basil, dill, cilantro, and mint — are abundant, along with bunched beets, carrots, and the season's first onions and garlic.
Choose firm, glossy squash and cucumbers without soft spots, beans that snap crisply, and melons that are heavy and fragrant at the stem. Store summer squash and cucumbers in the crisper and use within a few days; keep melons at room temperature until cut, then refrigerate.
For selection and storage: the desert's spring crops are at their last and best now, so enjoy the greens and peas before they vanish for the season. Keep herbs wrapped and refrigerated and cure fresh onions and garlic in a dry, airy spot. By June the low-desert markets thin under the heat until the monsoon and the high-country harvest revive them.
Night Sky This Month
May offers warm, dry, stable nights perfect for Arizona stargazing before the summer monsoon clouds arrive. The high-elevation dark-sky sites shine now — Flagstaff and Lowell Observatory, the Grand Canyon (whose popular Star Party is held in June), and the cool pine country of the Mogollon Rim — while Kitt Peak and the southern desert parks like Oracle State Park still offer warm comfortable observing. May's steady air is excellent for planetary and double-star viewing.
The sky is in its spring-to-summer transition. Leo and the galaxy-rich Virgo realm ride high after dark, the Big Dipper stands overhead with its handle arcing to orange Arcturus and on to Spica, and by late evening the summer keystone of Hercules and the brilliant Summer Triangle stars begin to rise in the east. The great globular cluster M13 in Hercules climbs into view for telescopes.
The Eta Aquariid meteor shower, debris from Halley's Comet, peaks in early May and favors the pre-dawn hours from a dark southern horizon. For this year's exact planet positions and the best moonless nights, see the printable Arizona night-sky guide.
Butterflies & Pollinators
May keeps Arizona's butterflies active despite the building heat, with the action shifting toward shaded canyons and watered gardens. Two-tailed and Western Tiger Swallowtails patrol the riparian corridors and city gardens, Pipevine Swallowtails work the canyon bottoms, and the Gulf Fritillary remains abundant on passionvine. Queens nectar at milkweed and desert broom, and clouds of sulphurs — Cloudless, Southern Dogface, Sleepy Orange, and Dainty Sulphur — drift over the desert flats.
The sky-island canyons hold their special butterflies now: Arizona Sister in the oaks, Mexican and Spring White, fast-flying duskywings and skippers, and an array of hairstreaks and blues along the streams. In the desert, the tiny Western Pygmy-Blue and Marine Blue stay busy in the saltbush flats.
To help them: as the desert dries, a watered garden with blooming lantana, milkweed, and desert lavender becomes a vital refuge — keep nectar flowers going and provide a shallow water or damp-sand spot for puddling. Plant passionvine and milkweed for the fritillaries and queens, and avoid insecticides while caterpillars are feeding.
What to plant for them is in the Arizona native plants guide
Trees This Month
May is the saguaro's moment. The giant saguaro cactus raises its crown of creamy night-blooming flowers — the state flower — opening in succession through the month, while the columnar organ pipe and senita cacti of the far south bloom too. The palo verde finishes its golden bloom and sets seed pods, ironwood and mesquite flower and begin forming the bean pods that will feed desert wildlife, and the desert willow keeps opening its orchid-like blossoms along the washes.
The high country comes fully into leaf. The quaking aspens on the San Francisco Peaks and the Mogollon Rim are in fresh green, the Gambel oaks have leafed out, and the ponderosa pines push their new candles and shed yellow pollen across the plateau. In the sky-island canyons, the Arizona sycamores, bigtooth maples, and Arizona walnuts shade the streams where the trogons nest. From the saguaro flats to the spruce-fir peaks, every life zone is now in active growth.
Weather & Daylight
Across Arizona, a typical May day averages a high near 83°F and a low near 51°F, with about 0.3 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Summer heat arrives fast, afternoons climbing into the low 80s under a nearly cloudless, bone-dry sky.
| Average high | 83°F |
|---|---|
| Average low | 51°F |
| Precipitation | 0.3 in |
| Sunrise (mid-month) | 5:26 MT |
| Sunset (mid-month) | 19:19 MT |
Figures are statewide averages over the 1991–2020 U.S. climate normals; local conditions vary with elevation and distance from the coast. Sunrise and sunset are computed for a midstate point on the 15th (MT).
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Same month elsewhere: May in Arkansas · May in California · May in Colorado