Exterior Painting Weather in St. George, UT: 10-Day Windows & Best Months

Q: What temperature can you paint outside?

50–90°F for standard formulas, 35°F+ for low-temp lines, and the wall itself must stay 5°F above the dew point. In St. George the practical range is set by nights: the 40°F overnight floor arrives around April and leaves after October.

Q: How many dry hours does exterior paint need before rain?

Plan 24 rain-free hours after the last coat; the engine fails any day that can't deliver them. With St. George's rain odds swinging from 5% of days in June to 19% in February, the strip above is mostly a search for that dry pair.

Q: Why does dew ruin fresh paint?

Fresh latex needs hours before it can take standing water; evening condensation gets there first on cooling siding. The check: air minus dew point from 6–11 p.m., 5°F or better. Humid February evenings in St. George are when GOOD afternoons hide failing nights.

Q: Can you paint in high humidity?

Up to about 80% daytime RH — above that, dry times stretch until the film meets the evening dew. 80–83% reads MARGINAL on the engine; more is a fail. Pair humidity with St. George's dew-point spread rule and paint mornings-into-early-afternoons in the humid months.

Q: What is surface temperature vs air temperature?

Two different numbers: air (what the app shows) and the wall (what the paint feels). Sun adds 20°F or more; evening radiational cooling subtracts. That's why the engine checks the 90°F top on St. George's hot afternoons and the dew-point spread after sunset — both are surface problems the air forecast hides.

Q: When does painting season end in St. George?

When nights stop clearing 40°F — in St. George that's typically after May, when average lows hit 56°F and falling. Low-temp formulas (35°F rated) buy a few extra weeks; the engine shows them as MARGINAL days before the hard close.

The exterior painting season in St. George runs March through May — 4 months averaging at least 8 workable days by NOAA 1991–2020 normals. The single best month is October, averaging 28 days that clear every check — highs of 79°F, lows near 47°F, and a 10% daily rain chance. Below: today through day 10 against the label rules, then the year at a glance.

GOOD — every label check passes MARGINAL — one soft fail NO — hard fail or several soft

The rules this check uses

These rows are what the St. George strip checks hour by hour: consensus paint-can requirements, plus the low-temp-formula band the engine marks MARGINAL.

Typical label thresholds for exterior painting — the ruleset behind every St. George verdict above.
Check	Threshold	Why it matters
Air temperature	50–90°F (low-temp formulas from 35°F)	The film (or mix) chemistry runs on temperature — both while you work and for the first hours after.
Overnight low	≥35°F during the first 24 h (≥40°F preferred)	Curing continues after dark; the first night can undo a perfect afternoon.
Dry before	≤0.05" rain in the prior 12 h; watch back to 24 h	Checked backward from your start hour using the two look-back days in the forecast data.
Dry after	<0.05" rain for 24 h after	The engine sums forecast rain hour by hour through the cure window for St. George.
Evening dew-point spread	≥5°F from 6–11 pm	When air temperature meets the dew point, water condenses on your fresh work first.
Daytime humidity	≤80%	Read as the daytime maximum, 10 a.m.–5 p.m.; within 3 points of the limit counts as marginal.
Wind	≤15 mph (brush only up to 20 mph)	Wind dries the leading edge too fast and carries overspray.

Always follow your product label — formulas vary. The table above is the typical range across major manufacturers, not a promise about your can.

Best months for exterior painting in St. George

St. George's calendar, scored: each month's days passing the temperature rules, discounted by that day's historical rain odds (NOAA 1991–2020). Not a forecast.
Month	Avg high	Avg low	Rain odds/day	Workable days
January	54°F	28°F	17%	0
February	59°F	32°F	19%	0
March	68°F	39°F	16%	10
April	75°F	46°F	11%	27
May	85°F	56°F	9%	24
June	96°F	64°F	5%	0
July	102°F	72°F	8%	0
August	100°F	70°F	10%	0
September	92°F	61°F	8%	7
October	79°F	47°F	10%	28
November	64°F	35°F	11%	1
December	53°F	28°F	15%	0

St. George compresses the whole exterior painting year into March through May. Miss those 97 workable days and the next real window is months out: by June, average lows hit 64°F against a 40°F floor. Plan the prep work in advance and treat every GOOD chip as spendable. The Utah table ranks every listed city by the same math.

July here fails on heat, not rain: the average high of 102°F sits over the 90°F label ceiling, and 31 of 31 days typically top 90°F. Midsummer work moves to dawn or waits for October.

If the walls pass, the roof might too: roof coating in St. George uses the same film chemistry with tighter dew and wind limits.

Source honesty: every monthly figure on this page is the 1991–2020 normal at St George, Ut Us, 5.5 km from St. George's center — your block's shade lines and wind exposure sit on top of that baseline. Scoring details are on the methodology page.

St. George by the numbers

Hottest month: July — 102°F average high, 31 days topping 90°F.
The cold floor is December at 53°F afternoons and 28°F overnight.
Measurable rain: February leads at 19% of days; June is the quiet end at 5%.
The 40°F-night season spans April–October here.
Bottom line for St. George: roughly 97 workable exterior painting days a year.

Prep checklist

Find application day plus 24 dry hours with nights at 40°F+; St. George offers that pairing most often in October (28 workable days).
Scrape, then wash: loose paint and chalk go first, because latex only grips solid substrate.
Give washed siding 24 hours — north walls in St. George can need double after a February-grade soak.
An ir surface thermometer settles arguments: label limits bind the wall surface, which outruns St. George's air by 20°F+ in sun.
Bare wood gets primer, stains get stain-blocker, gaps get caulk — in that order, on dry substrate.
Sequence walls so you always paint in shade; midday sun skins latex before it levels.
Cut in with an angled brush set, roll a wet edge, and drop the sprayer plan over 15 mph.
Stop 2 hours before sunset: with October lows near 47°F, St. George's siding meets the dew point before the late news.

Gear that saves a window

Transparency note: gear links here become affiliate links only when the program is enabled — today they are plain references. See the affiliate disclosure.

Angled brush set
Control at trim, corners, and cut-in lines.
Canvas drop cloths
Grips ladders and won't shred like plastic.
Extension pole
Second-story reach without moving the ladder every pass.
IR surface thermometer
Reads the wall, not the air — sun-baked siding runs hotter.

FAQ

What temperature can you paint outside?

50–90°F for standard formulas, 35°F+ for low-temp lines, and the wall itself must stay 5°F above the dew point. In St. George the practical range is set by nights: the 40°F overnight floor arrives around April and leaves after October.

How many dry hours does exterior paint need before rain?

Plan 24 rain-free hours after the last coat; the engine fails any day that can't deliver them. With St. George's rain odds swinging from 5% of days in June to 19% in February, the strip above is mostly a search for that dry pair.

Why does dew ruin fresh paint?