| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 36°F | 27°F | 1.1" |
| February | 26°F | 47°F | 36°F | 0.7" |
| March | 33°F | 58°F | 44°F | 1.2" |
| April | 37°F | 66°F | 51°F | 0.7" |
| May | 45°F | 76°F | 60°F | 1.2" |
| June | 53°F | 86°F | 69°F | 0.7" |
| July | 61°F | 97°F | 79°F | 0.1" |
| August | 57°F | 93°F | 75°F | 0.2" |
| September | 48°F | 83°F | 64°F | 0.4" |
| October | 38°F | 67°F | 51°F | 0.8" |
| November | 29°F | 50°F | 38°F | 1.1" |
| December | 20°F | 37°F | 28°F | 1.8" |
| Index | Ontario | Oregon | National |
| Air quality index | 36 | 32 | 42 |
| Pollution index | 1,647,310 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 293 |
| Days with moderate air quality | 60 |
| Days w/ poor A.Q. for sensitive groups | 9 |
| Days with unhealthy air quality | 3 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Nyssa, OR | 3,176 | 36 | 28.0% |
| Fruitland, ID | 5,390 | 36 | 28.0% |
| Vale, OR | 2,210 | 36 | 28.0% |
| New Plymouth, ID | 1,641 | 36 | 28.0% |
| Annex, OR | 246 | 36 | 28.0% |
| Ontario, OR | 11,031 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Middle Island, NY | 11,030 | 43 | 14.0% |
| Spencer, IA | 11,038 | 35 | 30.0% |
| Doctor Phillips, FL | 11,020 | 39 | 22.0% |
| Franklin Lakes, NJ | 11,044 | 51 | 2.0% |
| New Baltimore, VA | 11,017 | 38 | 24.0% |
| Ontario, OR | 11,031 | 36 | 28.0% |
Here are the best places to live in Oregon
Safest States In The US
Check out the 10 most dangerous cities in Oregon
See the best places to live in Ontario