As of late August 2025, monarch butterflies from northern U.S. and Canada have begun their fall, southward migration! They are heading towards their wintering grounds in the Oyamel fir forest of the Sierra Madre Mountains in central Mexico. By mid-August sightings had already been reported in Illinois, West Virginia and North Carolina.  Texas experiences the peak of migration in mid-October.  The migration is usually over by the end of October, with butterflies arriving at their wintering grounds in early November.

Monarchs migrate in generations.  The first 3 generations begin leaving Mexico in early March and begin their migration of nearly 3,000 miles up to the northern United States (Minnesota, Wisconsin, Michigan) and southern Canada (Ontario and Quebec). They only live 2 to 6 weeks and are focused on reproducing and laying eggs on milkweed plants. The first generation dies off by May but their offspring (second and third generations) persevere through the journey north, laying eggs as they continue their migration.

The last generation, a “super generation” of monarchs, returns nearly 3,000 miles from the north all the way down to the Monarch Butterfly Biosphere Reserve in central Mexico where they spend the winter. Although a typical monarch life span is 2 to 6 weeks, this super generation can live up to 9 months! They sense the winter months coming with the shorter days and changing temperatures. Milkweed, their food and nectar source, is also withering and losing its nutritional value. This triggers the monarch to go into diapause.

Diapause is a state of reproductive pause. To conserve energy for the long flight the monarch puts their reproductive system on hold.  They eat and store large amounts of fat during the caterpillar stage.  Their metabolism slows down, prompting a longer life span for the butterfly.  For them to reach their overwintering site they need to consume enough milkweed as caterpillars and nectar as adults, in order to survive while in hibernation.  It takes them up to 2 months to fly to Mexico!

With the right conditions a monarch can travel up to 100 miles in a single day.  These butterflies coast on air currents to fly quickly and conserve energy.  They often fly at elevations where we can’t even see them from the ground, at 800 to 1,200 feet high.  The monarch’s migratory pattern is the most highly evolved of any known species of its kind.  Monarchs have circadian clocks in their antennae and navigate using internal compasses that respond to the position of the sun and the earth’s magnetic field.

Once they arrive in Mexico they remain inactive, clustering in trees, conserving their energy reserves and staying warm.  When it starts to warm up, to at least 55 degrees, the sun warms

their wings and they can fly down to the ground to drink water for minerals and to prevent dehydration.  The arrival of warmer temperature in spring signals the end of diapause.  After about 4 months in Mexico, this super generation will then mate and migrate north to Texas to lay their eggs where the new first generation emerges from its chrysalis, and they start the cycle all over again.

The super generation has just started their long migration south and are headed our way!  They primarily travel through cities along the I-35 corridor, taking advantage of air currents, including the jet stream, to aid in their migration.  During the fall monarchs fly through Texas in a 300-mile-wide path stretching from Wichita Falls to Eagle Pass.  Monarchs enter the Texas portion of the flyway during the last days of September.  By early November most have passed through into Mexico.

During their long migration south, monarchs only travel during the day and stop for nectar along their way. To attract more monarchs into your garden on this last bit of their journey we need to have available to them an array of their favorite nectar plants.  Plant some native Texas milkweed: Antelope horn, Green and Swamp.  Other favorites are Aster, Goldenrod, Butterfly weed and Blue Mistflower.  Having these plants accessible to them will help sustain them through the winter months during their hibernation.  This gives them the strength to start it all over again in March of next year.

Although monarchs are not an endangered species, their numbers are in decline due to habitat loss, pesticides and climate change. The loss of milkweed, their only source of food for the caterpillar, the illegal logging of the Oyamel Forest and harsh weather patterns have contributed. Let’s do everything we can to help preserve the cherished monarch!