UV Index in Ontario, United States

Last updated: May 3, 2025

Understanding the UV Index is crucial for the residents of Ontario, United States, where outdoor activities and sunny days are plentiful. Being aware of the UV levels helps in preventing sunburn and maintaining skin health, essential for enjoying the great outdoors safely. Ontario’s Csb climate brings a unique blend of summer warmth and clear skies, making it important to monitor UV exposure, especially during peak hours when the UV Index soars to 10 around noon. By staying informed, you can protect your skin and make the most of your time in the sun!

Hourly UV Index in Ontario

The UV Index throughout the day presents a clear escalation and decline in sun exposure risk. Starting at a mild level 1 at 7:00 AM, it gradually climbs to a notable level 10 by noon, indicating peak midday sunlight intensity. The zenith occurs between 12:00 PM and 1:00 PM, where the index remains at 10, necessitating protective measures against harmful UV rays. As the afternoon progresses, the UV Index begins to taper off, dipping to level 7 by 3:00 PM and eventually returning to level 1 by 7:00 PM. To ensure skin health and safety, sun protection is essential during those high-risk hours around midday!

Average solar exposure data for the current time of the year. Actual values may vary and depend on many factors, such as cloud cover, vegetation cover, surface type, etc.
Time	UVI	Category	Time to Burn
07:00	1	low	45 min
08:00	2	low	45 min
09:00	4	moderate	30 min
10:00	6	high	25 min
11:00	9	very high	15 min
12:00	10	very high	15 min
13:00	10	very high	15 min
14:00	9	very high	15 min
15:00	7	high	25 min
16:00	5	moderate	30 min
17:00	3	moderate	30 min
18:00	1	low	45 min
19:00	1	low	45 min

Monthly UV Index Trends in Ontario

During the year, UV Index values show significant seasonal variation, peaking in the summer months. High-risk months for UV exposure include March through August, particularly notable in June and July, where the UV Index reaches an extreme level of 12 and 11, respectively, with a burn time of only 10 minutes. Visitors and residents are advised to take necessary precautions during these months, such as wearing protective clothing, using broad-spectrum sunscreen, and limiting sun exposure, especially between 10 AM and 4 PM. As UV levels decrease from September onward, with moderate levels returning in the winter months of November and December, maintaining sun safety remains important, especially during high-exposure periods.

Monthly Maximum UV Index for Ontario, United States

The monthly maximum UV Index (UVI) represents the highest UV radiation level recorded each month in Ontario. It measures the strength of ultraviolet radiation from the sun and helps assess the risk of sunburn and UV-related health issues.

Data source: Statistical UV Index data for Ontario, based on information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

Compare Ontario UV Index with Other United States Cities

The table above highlights how UV exposure in Ontario compares to other major locations across United States. This comparison helps travelers and residents better understand regional sun intensity and plan outdoor activities with sun safety in mind.

Ontario's solar exposure compared to other cities in United States. Generated using Copernicus Atmosphere Monitoring Service information.
	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Chicago UVI	3	4	6	8	9	10	10	9	8	6	4	2
Brooklyn UVI	3	5	6	8	10	10	9	9	8	6	4	2
New York City UVI	3	5	6	8	10	10	9	9	8	6	4	2
Los Angeles UVI	4	6	8	9	10	11	11	10	10	7	5	4
Ontario	4	6	8	10	10	12	11	10	10	7	5	4
Houston UVI	5	8	9	11	11	12	12	11	10	9	7	5