July 30, 2026. A heat dome is sitting on Arizona this weekend. Local forecasts have Phoenix near 116°F on Friday and Saturday (July 31 and August 1)—hot enough to tie daily records—under an Extreme Heat Warning for southern, central, and western Arizona through Sunday evening.

What’s forecast

Arizona weather desks (AZFamily, FOX 10 Phoenix, Arizona Republic) are calling for:

• Wednesday–Thursday: Phoenix climbs through the low-to-mid 110s (about 111°F Wednesday, ~113–114°F Thursday).
• Friday–Saturday: Forecast highs near 116°F, with a real chance of matching the calendar-day records.
• Sunday: Still extreme—forecasts near 115°F—before a slight easing early next week.
• Nights stay dangerous: overnight lows have been stuck in the upper 80s to low 90s. Phoenix recently matched its warmest overnight low on record (97°F) on July 24–25 mornings, then posted another very warm night later in the week.

Rain chances in the Phoenix Valley are near zero for several days. Dry ground under high pressure tends to run hotter, not cooler.

Regional context from national coverage (NPR / Fox Weather):

• This is described as the third major U.S. heat dome in about a month.
• Roughly 70 million people were under the broader heat footprint as the dome tracked from the South/Midwest toward the West.
• Las Vegas has been on a multi-day streak of highs at or above 110°F, with more triple-digit days expected.
• Forecast centers flag the wider Desert Southwest / Four Corners corridor—including parts of Southern California and Death Valley—for life-threatening weekend heat, with some outlooks mentioning highs in the high teens Fahrenheit above seasonal normals.

Heat vs UV

Heat warnings get the headlines. UV still runs alongside them when skies stay clear.

WHO’s protection line is UV index 3—Moderate, not High. At 8 and above, the practical guide tells people to avoid being outside during midday hours. Extreme starts at 11. EPA’s 8+ band is the same idea: extra protection, especially late morning through mid-afternoon. The higher the index, WHO says, the less time it takes for harm to occur. That is not a Phoenix forecast number.

South Florida is a useful contrast this same week. Boca Raton–area forecasts for late July into August 2 called for daily highs mostly in the low-to-mid 90s°F, heat-index / RealFeel values near 110–112°F on the worst humid days, peak UV Index values of 11.0–12.0 (Extreme) on several dates including July 26, July 28, and August 2, and unprotected midday exposure timed to skin damage in under about 15 minutes on Extreme UV days.

Arizona’s dry heat feels easier to stay out in than Florida humidity. That is the trap, not a discount.

Desert skies make the UV side worse to miss. EPA’s UV-index calculation treats clear skies as letting through virtually 100% of the UV that would otherwise arrive; scattered cloud about 89%, broken about 73%, overcast about 31%. Phoenix Valley rain chances are near zero for several days. That is the clear-sky case.

Overnight lows do not move that UV clock. Nights stuck in the upper 80s to low 90s—and a 97°F record-matching low—are a heat-recovery problem. Solar-noon UV still sits in WHO’s four-hour period around solar noon, often between local noon and 2 p.m. A 6 a.m. that still feels like bathwater is a heat warning, not an 11 a.m. burn reading. A 4 p.m. at 116°F is worse for heat stroke than for peak UV—and still a protection window. That lag is UV peaks before the heat.

Heat tells you whether your body can cool. UV tells you how fast unprotected skin burns. This weekend in Phoenix, you need both answers.

Through Sunday

If you are in metro Phoenix or under the Arizona Extreme Heat Warning:

1. Treat Friday–Sunday midday as a no-go for long outdoor work unless it is essential and shaded.
2. Move exercise, errands, and kids’ outdoor time to early morning—before the daily climb into the 110s.
3. Do not trust overnight “cool-down.” Lows in the 90s mean your body may not fully recover between days.
4. Check live UV as well as temperature on the homepage. Clear desert sun still sits in Very High / Extreme bands this time of year.
5. Hydrate and watch heat-stroke signs (confusion, severe fatigue, nausea, headache). Heat stroke is a medical emergency; UV planning does not replace cooling someone fast.

If you are elsewhere under the shifting dome (Four Corners, Southern California deserts, lingering Gulf/South humidity), use the same rule: read the alert for your county, then check today’s UV peak before you commit to midday sun. Coverage has framed recent U.S. heat pulses as unusually persistent. For readers here: when a city is chasing record 116°F highs, outdoor time breaks into short, protected windows.

Sources

Arizona forecasts and the Extreme Heat Warning as of 30 July 2026: local desks (AZFamily, FOX 10, Arizona Republic) and National Weather Service Phoenix. National heat-dome framing from NPR / Fox Weather. WHO protect-from-3, midday caution at 8+, Extreme at 11+, four-hour maximum around solar noon: UV index Q&A and Global Solar UV Index: a practical guide. Higher index, less time to harm: WHO ultraviolet radiation fact sheet. EPA 8+ extra-protection band: UV Index Scale. Clear-sky UV near 100%, scattered 89%, broken 73%, overcast 31%: EPA, Learn About the UV Index. Prefer the latest NWS product for your county. Forecasts change.