Bismarck, ND UV Index: Hour by Hour

Q: What is the UV index in Bismarck right now?

This page reads the NOAA/EPA hourly forecast for Bismarck live from EPA Envirofacts every time it loads, so the curve above is today's official forecast with its date attached. The daily maximum lands at solar noon. As climatological context, a typical October midday forecast here is 2.3.

Q: What time is UV strongest in Bismarck?

The peak of the curve sits at solar noon, which on clock time falls around midday to early afternoon depending on daylight saving time and where Bismarck sits in its time zone. EPA's protection messages repeatedly name the window between late morning and mid afternoon; the hourly chart above shows today's exact shape rather than a rule of thumb.

Q: When does the high UV season start in Bismarck?

In the 2015 to 2024 bulletin record, June is the first month whose typical midday forecast reaches 6, the High category, and the season runs through August. The peak month is July, averaging 7.6.

Q: How high has the UV index been in Bismarck?

The highest value NOAA published for Bismarck in the 2015 to 2024 archive is 10, which sits in the Very High category. The "highest seen" column of the monthly table shows the record for each month of the year.

Q: Is the UV forecast for Bismarck accurate on cloudy days?

The NOAA computation starts from clear-sky UV and then adjusts for the cloud cover the weather models expect, so cloud is already in the number you see. What people get wrong is the direction of the error in their heads: EPA notes that up to 80 percent of solar UV radiation can penetrate light cloud cover, so an overcast sky is nowhere near an SPF.

Q: Who publishes the Bismarck UV forecast?

The NWS Climate Prediction Center issues the UV index forecast each afternoon for Bismarck and 57 other US cities, valid the next day at solar noon, and EPA republishes it through the Envirofacts API this page reads. The scale and the protection messages are the WHO Global Solar UV Index as adopted by EPA and NWS. The monthly figures on this page are our averages of those published values.

Today's NOAA/EPA UV forecast for Bismarck, reproduced as issued, with the ten year monthly climatology behind it.

Reading today's hourly UV forecast for Bismarck…

Peak month

July

Typical July midday UV

7.6

Highest on record 2015-2024

Bismarck, ND today

Live · NOAA/EPA UV forecast

…

forecast peak today

EPA feed unavailable

…

hours at 6+ (High)

in today's forecast

…

hours at 8+ (Very High)

in today's forecast

2.3

typical October midday UV

2015 to 2024 climatology

Bismarck has one of the shorter UV seasons in the lower 48, but its long June and July days keep the sun at burning strength for more hours than the latitude suggests.

The curve, not the number

Today’s hourly UV forecast for Bismarck

The single number in a weather app is the day’s solar noon maximum. What it cannot tell you is that the same day is usually harmless at 8 AM and still strong at 3 PM. The curve below is the NOAA/EPA hourly forecast, exactly as published: plan hard outdoor time on its shoulders and treat the hours around the peak as the protection window.

Reading the NOAA/EPA hourly UV forecast for Bismarck…

Where every number here comes from. Live values are the NOAA/EPA UV index forecast, issued daily by the NWS Climate Prediction Center and read in your browser from EPA Envirofacts, reproduced as published with the forecast date shown. Monthly climatology is computed from CPC’s archived daily bulletins, 2015 to 2024. Protection guidance is quoted verbatim from EPA and WHO with attribution.

Month by month

Bismarck UV climatology, 2015 to 2024

Ten years of NOAA CPC’s archived daily bulletins for Bismarck, aggregated by month. This is the planning layer: it tells you when the High and Very High seasons open and close here, and how often the top of the scale actually appears.

Monthly UV index climatology for Bismarck
Month	Typical midday UV	Days 6+ (High)	Days 8+ (Very High)	Days 11+ (Extreme)	Highest seen
Jan	1.2	0%	0%	0%	2
Feb	2.2	0%	0%	0%	4
Mar	3.5	0%	0%	0%	6
Apr	4.5	27%	0%	0%	8
May	5.7	59%	18%	0%	9
Jun	7.2	81%	59%	0%	10
Jul	7.6	91%	66%	0%	10
Aug	6.2	76%	19%	0%	9
Sep	4.4	18%	0%	0%	7
Oct (now)	2.3	0%	0%	0%	4
Nov	1.3	0%	0%	0%	3
Dec	1	0%	0%	0%	1

Computed from NOAA Climate Prediction Center daily UV index bulletins for Bismarck, 2015 to 2024. “Typical midday UV” is the mean of the daily solar noon forecasts; the day-share columns are the percentage of archived days at or above each WHO category threshold; “highest seen” is the highest value CPC published for the city in the period. Simple aggregation of the agency’s numbers, nothing modeled.

Sun visible as a bright disc through a thin, even layer of cirrostratus cloud — The forecast already accounts for cloud, and thin cloud does far less than it looks like it should. EPA: “Sunburn is possible on a cloudy day. Up to 80% of solar UV radiation can penetrate light cloud cover.” “Cirrostratus clouds obscuring the sun along Old Ox Road, Sterling, Virginia” by Famartin, CC BY-SA 4.0

Reading the number

The scale, in EPA’s words

1-2Low

“Wear sunglasses on bright days. In winter, reflection off snow can nearly double UV strength. If you burn easily, cover up and use sunscreen.”

3-5Moderate

“Take precautions, such as covering up and using sunscreen, if you will be outside. Stay in shade near midday when the sun is strongest.”

6-7High

“Protection against sunburn is needed. Reduce time in the sun between 11 a.m. and 4 p.m. Cover up, wear a hat and sunglasses, and use sunscreen.”

8-10Very High

“Take extra precautions. Unprotected skin will be damaged and can burn quickly. Try to avoid the sun between 11 a.m. and 4 p.m. Otherwise, seek shade, cover up, wear a hat and sunglasses, and use sunscreen.”

11+Extreme

“Take all precautions. Unprotected skin can burn in minutes. Beachgoers should know that white sand and other bright surfaces reflect UV and will increase UV exposure. Avoid the sun between 11 a.m. and 4 p.m. Seek shade, cover up, wear a hat and sunglasses, and use sunscreen.”

Quoted verbatim from EPA, A Guide to the UV Index (EPA430-F-04-020, May 2004).

The categories above stand in for a burn-time table, which EPA’s guide to the index rules out: “Relating UV Index values to "time to burn" or "safe tanning time" sends an incorrect and potentially harmful message to the general public. The UV Index should not be used to suggest that unprotected exposure is risk-free.” And on the other end of the scale, WHO notes that “even for very sensitive fair-skinned people, the risk of short-term and long-term UV damage below a UVI of 2 is limited, and under normal circumstances no protective measures are needed”.

Skiers on a high open snow slope at Breckenridge, Colorado under strong sun — Surfaces change the dose without changing the forecast number: EPA notes snow may reflect as much as 80 percent of UV, sand 15 percent, and water 10 percent. Breckenridge, Colorado. “Colorado 2013 (Breckenridge ski area)” by Jeff Gunn, CC BY 2.0

Saguaro cactus and desert scrub in front of the Superstition Mountains under a bright, nearly cloudless sky — Shade is the first tool the agencies recommend, and the desert shows why it matters that there often is none. WHO: “Even a long stay in open shade, for example between buildings, may give a sensitive person a sunburn on a day with high UV levels.” “Superstition Mountains” by lydia_pirate, CC BY-SA 4.0

Common questions

Bismarck, ND UV index FAQ

What is the UV index in Bismarck right now?

What time is UV strongest in Bismarck?

When does the high UV season start in Bismarck?

How high has the UV index been in Bismarck?

Is the UV forecast for Bismarck accurate on cloudy days?

Who publishes the Bismarck UV forecast?

Keep planning

Beyond Bismarck

North Dakota UV indexThe statewide page: every North Dakota bulletin city, the season window and the monthly tables in one place.North Dakota tick forecastSunny-hour trips end in brushy parking-lot edges. Check the tick picture before you go.North Dakota mosquito forecastWhen the UV curve drops to zero at dusk, the mosquito curve takes over.

UV index in other cities

Hourly and daily values on this page are the NOAA/EPA UV index forecast for Bismarck, read live from EPA Envirofacts and reproduced as published with the forecast date shown. Monthly climatology is computed from NOAA CPC’s archived bulletins, 2015 to 2024. Guidance is quoted verbatim from EPA and WHO.
Hero image: “White Cumulus Clouds against Blue Sky with Sun Shining” by Vanlewen, CC BY-SA 4.0