What kind of weather might you expect at Zion National Park throughout the year? It's a mixed bag, ranging from high heat in the summer to mild falls, comparatively mild winters (when compared to, for instance, Glacier National Park), and wet springs.

According to park staff:

Spring

March and April - Spring break in canyon country

Conditions

As the daylight and warmer weather return to Zion, the trees begin to grow leaves and the earliest wildflowers begin to bloom. Daytime temperatures are warming but nights can still be cold. The daily temperature swing can be 30°F (-1°C) or more. Depending on the amount of snow we received over the winter, higher elevation areas may still be inaccessible without winter gear. Snow begins to melt and raises the level of the river so the Narrows may be closed for an extended period.

Summer

May through September - See lots of the park...and other visitors!

Conditions

Summer is hot with temperatures regularly over 100°F / 38°C. Use a refillable water bottle to carry plenty of water with you. There are places to refill marked on the park map. You should take measures to avoid heat illness while you are visiting. Your safety is your responsibility. When summer Monsoon begins, (July-September) watch out for flash floods. Ask about the risk at the Visitor Center.

Fall

October and November - Same amazing scenery, slightly calmer pace.

Conditions

Cooler conditions make it more pleasant to hike but layers may be necessary to deal with the changing temperatures. High and low temperatures can vary by 30°F (-1°C) each day. Fall colors begin to show at the highest elevations, slowly making their way down to Zion Canyon at the end of October and early November.

Winter

December, January, and February - Solitude and snow (sometimes).

Conditions

Winters in Zion National Park are cold and often wet. Temperatures can range from highs of 50°F - 60°F (10°C  - 15.6°C) during the day to lows well below freezing at night. Nearly half of the annual precipitation in Zion Canyon falls between the months of December and March. Roads are plowed, but certain trails may be closed due to the hazard of falling ice. After winter storms, snow typically disappears within a matter of hours at lower elevations. At higher elevations, the snow accumulates. Icy conditions may exist on trails, especially anywhere that stays in the shade. We recommend traction devices for your boots to reduce the risk of slipping. The Narrows will be cold and you will likely need a drysuit to hike safely.

A winter morning along the Big Bend, Zion National Park / Rebecca Latson