The Southwest U.S. offers some of the most spectacular terrain in the world for outdoor adventures. During the spring and fall months when mud and snow limit outdoor recreation further north, the Southwest U.S. is at its prime due to mild temperatures and infrequent precipitation.

Hiking, climbing, mountain biking, and camping are just a few of the world-class activities you can enjoy in the Desert Southwest during the spring and fall. 

The Southwest is filled with public lands, including numerous national parks and monuments. We recently added an interactive Public Lands Map (available on the web currently, coming soon to the app) that you can use to explore some of the parks, forests, and other accessible areas. 

Southwest Weather – Overview

Weather conditions are typically best from March to May, and again from late September to November, while the summer months are less ideal due to extreme heat and frequent afternoon thunderstorms that lead to lightning and flash flooding hazards.

While most people head to the desert to escape bad weather in the spring and fall, that doesn't mean you should ignore the weather forecasts. Weather patterns can still vary substantially during the spring and fall with temperature changes and occasional precipitation. 

Also, elevation plays a significant role in weather across the Southwest. The deeper canyons can dip as low as 2,000 feet in elevation while the higher terrain of Northern Arizona and Southern Utah extends up to 12,000 feet in elevation and can receive snow late in the spring and early in the fall.

Spring Weather Patterns (March to May)

Winter is a relatively wet season for the Southwest as organized storm systems track across the region from November to February, bringing widespread precipitation. During the spring, these storm systems become less frequent over time from March to May, and precipitation events tend to be lighter and short-lived.

Also, temperatures are warming up during the spring and it can be a wonderful time of year to visit the desert while the high mountain regions to the north are still snowbound. 

Storm systems still move through from time to time through April, bringing rain and high-elevation snow along with colder temperatures. Storms typically become weaker and less frequent by May, producing scattered showers and occasional thunderstorms more so than widespread precipitation.

Rivers and streams can occasionally be flood-prone during the spring due to snowmelt from higher terrain.

While spring tends to be a drier season, winds are often a factor. This is due to the change in seasons in which temperature gradients (and pressure gradients) are sharper between warm and cold air masses, which leads to stronger winds.

Also, the atmosphere is better "mixed" during the spring thanks to the stronger sun and warmer temperatures at the surface. This allows for stronger winds at higher altitudes to transition down to lower altitudes with daytime heating and explains why springtime winds are usually stronger in the afternoons.

Summer Weather Patterns (June to September)

Summer weather is more extreme in the Southwest as temperatures become very hot across most of the region. June is the driest month of the year in the Southwest and is often the hottest as cloud cover relief is uncommon.

From July to September, the seasonal North American Monsoon develops, in which subtropical moisture arrives from the south, resulting in frequent afternoon thunderstorms. Lightning becomes a regular hazard, and heavy downpours from storms pose a flash flooding risk in slot canyons and dry washes.

Fall Weather Patterns (Late September to November)

The monsoon typically starts to wind down by late September or early October and temperatures also begin to cool down by this point in the season. As a result, the fall season is another excellent time to visit the Southwest with more comfortable temperatures and less frequent rainfall.

However, storm systems do start to move through periodically in the fall. While sunny multi-day dry stretches are typical in between storm systems, when storm systems do move through they tend to produce heavier rainfall compared to the spring months. Higher terrain can also see snow as early as October.

Forecasting Tools

There are numerous weather factors to take into account when planning a spring or fall desert trip. We offer point forecasts for any location and elevation in the world to help you plan your trip around the weather. 

Tap on the search icon at the bottom of the app or the search bar at the top of the website. From here, you can enter the name of the town, park, trail, etc.

 Once the location pops up, select it and add it to your Summer Favorites List.

Is the location you entered not showing up in our search results?

Not to worry, as you can view and save custom points forecasts using our Forecast Anywhere feature.

Go to Maps, and then use our interactive map to zoom, point, and tap anywhere on the map you would like a forecast for. The elevation and lat-long of the point will display, and you can also name your custom point and save it to your favorites.

Weather Tab

Once you have the forecast page for a location pulled up, make sure you select the Weather tab as this will display the most relevant information for warm-season trail activities (as opposed to skiing or winter sports).

This view will display the current estimated weather (based on our forecast data) along with 10-day and hourly forecasts for numerous weather variables.

Temperature

While we normally think of the desert as being a warm place, temperatures can vary substantially in the Southwest U.S. and it's important to be prepared.

During clear weather in the spring and fall, large diurnal temperature fluctuations are typical with warm days and chilly nights. Frontal systems can often lead to significant temperature drops after several days of warm weather. 

Also, elevation plays a major role. During clear weather, daytime temperatures (late morning to afternoon) typically decrease about 5ºF for every 1,000 feet of elevation gained. 

Under the 10-Day Forecast, you can quickly view the high and low-temperature forecasts for each day. For hourly forecasts, select the relevant day and then tap on the Temp tab underneath the daily forecast.

Next to Temp, you can tap on "Feels Like" which shows you what the temperature will feel like, based on a formula that accounts for wind speeds in cooler weather and humidity in warmer weather.

Also, we display hourly temperature forecasts out to 2 days in our high-resolution temperature map overlay. This is based on data from NOAA's high-resolution weather model. This gives a good idea of how temperature changes by location, elevation, and time.

View → Temperature Map

Precipitation

Under the 10-Day Forecast, select Precip % to view hourly rain probability for any of the next 10 days. This will give you an idea of what time of day rain is more or less likely.

We also display the forecast rainfall amount for each day underneath the hourly graph.

You can also use our Radar and Forecast Radar map overlays to track rainfall.

Our Radar map shows current radar with the ability to loop back in time over the past 3 hours. While this is a great tool, keep in mind that terrain can interfere with radar beams and as a result, radar is not always representative of reality in complex terrain.

Our Forecast Radar map displays the projected radar over the next 2 days, and this is based on data from NOAA's high-resolution radar.

This is not always perfect in the case of pop-up "random" showers and thunderstorms, but it still gives a good general idea of what to expect in terms of movement and coverage of showers. This product also tends to be more accurate during widespread precipitation events. 

View → Current Radar Map

View → Forecast Radar Map

Snowfall & Snow Depth

We denote precipitation type when snow is expected, as this does occur across higher terrain in the Southwest in the spring and fall. Purple bars are displayed when mixed precipitation is forecast, and blue bars are displayed when snow is forecast. Green bars are displayed when rain is forecast.

Forecast snowfall amounts are displayed underneath the hourly precipitation graph, as is forecast liquid-equivalent precipitation (in purple) when mixed precipitation is expected. 

You can also view more detailed snow information, such as snow levels (the forecast rain/snow line), by tapping on the Snow Summary tab at the top of the screen.

If you are wondering about snow on the ground and whether or not it will impact hiking or biking conditions, you can use our estimated snow depth map. This map overlay gives a good general idea on whether or not you should expect snow on a given trail. 

View → Snow Depth Map

Wind 

Winds are often a factor in the spring and fall, which can offer relief on hot days or add to the chill factor on cooler days. Wind forecasts tend to vary by elevation, so it's a good idea to check the wind forecast for multiple locations depending on your plans and activities. 

Swipe left on the list of weather variables to find the wind forecast. We display sustained wind speeds with blue bars and wind gusts in red bars. At the top of each bar, we display the wind direction (where the wind will be blowing from), sustained wind speed, and wind gust denoted by "G".

We also have a map overlay for forecast wind gusts for the next 2 days. You can use this overlay to get a good idea of how winds will vary with elevation and over time.

View → Wind Gust Map

Cloud Cover

We also display hourly cloud cover forecasts out to 10 days. This can affect comfort levels in sun-exposed terrain, and can also impact photography conditions. 

We also have an hourly cloud cover map overlay, which displays forecast cloud coverage over the next 2 days.

View → Cloud Cover Map

Humidity

You can view hourly relative humidity to get an idea of how much moisture is in the atmosphere. Humidity is typically higher in the mornings (when temperatures are cooler) and lower in the afternoons (when temperatures are warmer).

Lightning

Lightning in the Southwest is most common during monsoon season in July and August and to a lesser extent September. However, thunderstorms occasionally happen in the spring (April and May) and infrequently during the fall (October).

Swipe left over the weather variables and then tap on the Lightning tab to view hourly lightning forecasts for any given day. This will give you a good idea of the timeframes in which lightning is most likely. Note that even when "Low Chance" is displayed, you should still factor this into planning and decision-making.

If you are lucky enough to have service while outside, you can also use our Lightning Density map to view lightning activity over the past 3 hours.

Note that while this map is useful for tracking storms, it should not be solely relied upon and you should be paying attention to the skies overhead as well.

View → Lightning Density Map

Flash Flood Risk

The Southwest is susceptible to deadly flash flooding because the dry soils and rocky terrain are unable to absorb heavy rainfall rates, and runoff can quickly occur in narrow canyons and dry washes in a matter of minutes.

Flash flooding is most common during monsoon season from July to September. However, it can occasionally occur in the spring due to the combination of rain and snowmelt, and also during the late fall when organized storm systems bring widespread heavy rain.

Our daily and hourly forecasts are a good starting point to get an idea of whether or not significant rainfall is a threat.

The National Weather Service issues Flash Flood Watches (for potential) and Flash Flood Warnings (when flooding is imminent) and is a good resource if you are heading into canyon country. 

The National Weather Service office in Salt Lake City also issues an excellent flash flood product every day from May 1 to October 31.

In addition, NOAA's Excessive Rainfall Forecast is a good resource to get an idea of whether or not heavy rainfall is a threat on a given day. 

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Questions? Send an email to [email protected] and we'll respond within 24 hours. You can also visit our Support Center to view frequently asked questions and feature guides.

Alan Smith