Month by month
Las Vegas weather in August
Nearly as hot as July, with monsoon storms and flash-flood risk.
At a glance
August is a close second to July for heat, with almost every day reaching the 90s and most reaching 100°F. The monsoon is usually active: the NWS says storms tend to build over the mountains around the valley and move in, bringing gusty winds, lightning and heavy bursts of rain that send water down dry washes. Humidity is higher than early summer, which makes the heat harder on the body.
By NOAA’s 1991–2020 normals for Harry Reid International Airport, August days peak around 103°F and nights bottom out near 81°F. An average August has 24.5 days at 100°F or hotter and 30.4 days at 90°F or hotter. Normal rainfall is 0.32 inches, with 2.2 days getting at least a hundredth of an inch and 0.7 days getting a tenth of an inch or more. The median August total is 0.22 inches, so in a typical year it is drier than the average suggests: a few wet years pull the average up.
Through the day
Get outside early. The coolest hour is around 6 a.m. at 81°F on average, and by 10 a.m. the normal temperature has already reached 90°F. The afternoon peak, around 4 p.m., averages 101°F, and on one afternoon in ten it tops 108°F. Evenings cool slowly: 9 p.m. still averages 94°F, so a late walk is warm but far easier than mid-afternoon.
| Time (PDT) | Normal | Cool day | Hot day |
|---|---|---|---|
| 6 a.m. | 81°F | 75°F | 87°F |
| 9 a.m. | 88°F | 82°F | 94°F |
| Noon | 97°F | 90°F | 102°F |
| 3 p.m. | 101°F | 94°F | 107°F |
| 6 p.m. | 100°F | 92°F | 107°F |
| 9 p.m. | 94°F | 87°F | 100°F |
| Midnight | 88°F | 82°F | 94°F |
"Cool day" and "hot day" are NOAA’s 10th and 90th percentiles for that hour: one August day in ten is cooler or hotter than shown. NOAA publishes hourly normals in standard time; we shifted them to clock time for daylight saving time. Hourly averages run a little below the normal daily high because the hottest moment doesn’t land on the same hour every day.
Humidity is up: the average dew point across the day is about 44°F, well above early summer, because monsoon moisture has arrived. Sweat evaporates more slowly, so the heat is harder on the body. Wind averages 8.3 mph over the day and is usually strongest around 6 p.m. (11.1 mph on average).
Over the month
August isn’t one temperature. The normal high falls from 104.4°F on August 1 to 100.3°F on August 31, and the normal low goes from 82.4°F to 77.8°F. That’s a small change, so the whole month feels much the same.
For a specific date, the live National Weather Service forecast on our home page is more useful than any average once you are within a week of your trip.
What to pack
- Light, loose clothing and a wide-brimmed hat
- Sunscreen, sunglasses and plenty of water
- A compact umbrella or rain shell for a sudden storm
- A light layer for indoor air conditioning
Staying safe
Heat. Heat is the deadliest weather hazard in the Southwest, according to the NWS. Drink water before you feel thirsty, avoid strenuous activity in the afternoon, and know the warning signs: heavy sweating, cramps, dizziness and nausea point to heat exhaustion, while confusion and hot skin can mean heat stroke, which is a 911 emergency. Our heat-safety guide has the NWS first-aid steps and where to find cooling stations.
Monsoon storms and flash floods. Storms often start over the mountains and send water into the valley’s washes and low streets, sometimes miles from where the rain fell. Never drive into a flooded road: the NWS says about a foot or two of moving water can float most vehicles. Stay out of washes and tunnels during and after storms, and when thunder roars, go indoors.
For current watches and warnings, follow the NWS Las Vegas office. Our resources page lists the other agencies worth knowing. In an emergency, call 911.
August records
| Record | Temperature | Date |
|---|---|---|
| Hottest | 116°F | Aug 3, 1979 |
| Coldest | 54°F | Aug 3, 1937 |
| Warmest night | 92°F | Aug 1, 2020 |
| Coolest day | 74°F | Aug 18, 1983 |
NWS Las Vegas records since January 1, 1937. Where a record has been tied, we show the most recent date. See every month on our records page.