UV Index in Ontario, United States

Last updated: August 1, 2025

Understanding the UV Index is crucial for residents of Ontario, United States, especially during the peak summer months when ultraviolet radiation levels can soar. With indices reaching as high as 10 around midday, awareness of UV levels is essential for preventing sunburn and protecting skin health. Ontario's Csa climate brings warm summers and increased sun exposure, heightening the risk of skin damage if precautions aren't taken. By staying informed about UV Index readings, residents can enjoy the beautiful outdoors while safeguarding their well-being.

Hourly UV Index in Ontario

The UV Index throughout the day reveals a striking increase in sun intensity as the morning transitions into afternoon. Starting off at a mild 1 at 07:00 and 08:00, it gradually escalates to 2 by 09:00. The real surge occurs between 10:00 and 13:00, where values leap to a peak of 10 at 13:00, indicating a significant risk of harm from unprotected sun exposure. As the afternoon wanes, the index dips from 10 at 14:00 to 8 by 16:00, before finally settling back to a more manageable 3 by 18:00 and 2 by 19:00. Be sure to take precautions when the sun's rays are at their strongest!

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	1	low	45 min
09:00	2	low	45 min
10:00	4	moderate	30 min
11:00	6	high	25 min
12:00	8	very high	15 min
13:00	9	very high	15 min
14:00	10	very high	15 min
15:00	9	very high	15 min
16:00	7	high	25 min
17:00	5	moderate	30 min
18:00	3	moderate	30 min
19:00	1	low	45 min

Monthly UV Index Trends in Ontario

Throughout the year, UV Index levels show notable seasonal changes, indicating varying levels of risk for sun exposure. The highest UV risk months are from May to September, with peak levels reaching 11 in June, categorizing this period as extreme, where the burn time is as short as 10 minutes. In contrast, the winter months of January, February, October, and November see moderate levels with an index ranging from 2 to 4, allowing for longer exposure times of 30 minutes before burns occur. As such, visitors and residents are advised to take extra precautions during high-risk months, especially in the summer, by wearing protective clothing, applying broad-spectrum sunscreen, and seeking shade when necessary to minimize the risk of skin damage.

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
Ontario	3	4	6	7	10	11	10	10	8	5	4	2
Los Angeles UVI	4	6	8	9	10	11	11	10	10	7	5	4
Houston UVI	5	8	9	11	11	12	12	11	10	9	7	5