When Can I Be Outside?

Hour-by-hour windows for outdoor time in St. George's desert heat, read on the National Weather Service scale.

About these tools

Hour by hour, when it is easier or harder to be outside in St. George. Summer here is genuinely dangerous: July 2024 averaged a 107.9°F high and the record is 117°F, so the workable hours are early morning and after sundown. This page reads the heat on the National Weather Service scale and says "easier" or "harder" — never "safe." When the heat is extreme, follow the official forecast and warnings below.

Today, Sunday, August 23

Best windows today: before 9 am.

Air in those windows is Moderate, not Good — acceptable for most people by the EPA’s scale, but anyone unusually sensitive to air pollution may want to take it easier.

As of August 23 at 7:49 PM. Modelled forecast for the area around central St. George, refreshed about every half hour.

Hour by hour today

5–6 amMostly fineAQI up to 51 (Moderate).
6–9 amComfortableNothing flagged on either scale.
9–11 amMostly fineFeels like up to 89°F (NWS Caution).
11 am–1 pmHarder goingFeels like up to 102°F (NWS Extreme Caution).
1–3 pmHarshFeels like up to 106°F (NWS Danger).
3–8 pmHarder goingFeels like up to 103°F (NWS Extreme Caution).
8–11 pmMostly fineFeels like up to 89°F (NWS Caution), and AQI up to 76 (Moderate).

UV peaks near 8 today. On the EPA’s UV index scale, 1–2 is low; 8 and above is very high to extreme and calls for extra sun protection.

The next two days

Day	Best windows	Peak feels-like	Peak air
Monday, August 24	before 9 am	103°F	70 · Moderate
Tuesday, August 25	before 9 am	101°F	49 · Good

Guidance, not a medical call

Heat lands differently person to person — age, pregnancy, some medications, working outdoors, and conditions like asthma all change the math. This page only ever says easier or harder, never “safe.” For health guidance see the official heat-safety pages, and for official readings use the channels listed below.

How this page decides

Heat uses the National Weather Service’s heat-index categories, applied to the modelled feels-like temperature: Caution 80°F–90°F, Extreme Caution 90°F–103°F, Danger 103°F–124°F, Extreme Danger 125°F and up.

Air uses the US EPA air quality index: Good 0–50, Moderate 51–100, Unhealthy for Sensitive Groups 101–150, Unhealthy 151–200, Very Unhealthy 201–300, Hazardous above that. The number here is that same EPA index, computed by Open-Meteo from the Copernicus CAMS model.

Each hour takes the harder of the two constraints, and the strip says which one. A “best window” means hours where the feels-like temperature stays below 80°F (below the NWS Caution band) and the air is no worse than Moderate — the EPA’s general-population activity cautions start at 101. No thresholds on this page are ours.

Reading it for your plans

The cool hours

The bearable hours in a Mojave-edge summer are right after dawn and after the sun drops. Locals clock trail runs, dog walks, golf and pickleball to the morning for a reason — by midday the pavement and red rock radiate heat long after the air temperature peaks.

Working and training outdoors

Construction crews, landscapers, and the city's heavy running and triathlon scene all face the same clock. This page shows when the heat eases, so the hardest efforts and outdoor shifts can be set for the least punishing parts of the day, with water before you feel thirsty.

Kids and older neighbors

About a fifth of St. George is over 65 and almost a quarter is under 18 — the two groups heat hits hardest. On extreme-heat days, check on older neighbors who live alone, and never leave children or pets in a parked car, which heats up far faster than the outdoor reading.

Worth knowing

Mojave Desert heat at 2,800 feet

St. George sits on the edge of the Mojave Desert in a hot-desert (BWh) climate: 100°F-plus summers, about 8 inches of rain a year, and roughly 255 sunny days. The dry air means shade and nightfall bring real relief, but daytime sun on sand, sandstone, and lava rock pushes surface heat well past the air temperature.

Source: NWS Salt Lake City, checked 2026-06-24

Who feels the heat first

Heat illness builds before it shows. The CDC notes infants and young children, people over 65, those with heart, lung, or kidney conditions, and anyone working or exercising outdoors are most at risk. Drink water on a schedule rather than by thirst, rest in shade or air conditioning, and learn the signs of heat exhaustion and heat stroke.

Source: CDC — Extreme Heat, checked 2026-06-24

The official channels

NWS Salt Lake City — local forecast and heat warningsThe official National Weather Service forecast and any Excessive Heat Watches or Warnings for the St. George area. When this page and the forecast disagree, follow the NWS.

Fetched August 23 at 7:49 PM. These are modelled estimates for the area around central St. George, not measurements — a shadeless trail at 3 pm runs hotter than the area-wide number. Weather and air-quality data by Open-Meteo (CC BY 4.0); air quality based on Copernicus CAMS. Heat categories from the National Weather Service; air bands from the US EPA.