| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 35°F | 27°F | 5.4" |
| February | 16°F | 35°F | 27°F | 5.1" |
| March | 24°F | 44°F | 35°F | 7.4" |
| April | 37°F | 61°F | 50°F | 6.5" |
| May | 46°F | 70°F | 60°F | 4.0" |
| June | 59°F | 82°F | 71°F | 5.1" |
| July | 63°F | 84°F | 74°F | 6.9" |
| August | 61°F | 84°F | 74°F | 5.1" |
| September | 52°F | 78°F | 67°F | 8.7" |
| October | 46°F | 65°F | 56°F | 15.5" |
| November | 31°F | 51°F | 41°F | 6.2" |
| December | 21°F | 36°F | 29°F | 5.2" |
| Index | Granby | Massachusetts | National |
| Air quality index | 40 | 40 | 42 |
| Pollution index | 7,859,360 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 305 |
| Days with moderate air quality | 59 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.320% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Westfield, MA | 41,303 | 40 | 20.0% |
| Holyoke, MA | 40,161 | 40 | 20.0% |
| Easthampton Town, MA | 15,930 | 40 | 20.0% |
| Northampton, MA | 28,552 | 40 | 20.0% |
| Agawam Town, MA | 28,627 | 40 | 20.0% |
| Granby, MA | 1,183 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Cave Spring, GA | 1,183 | 44 | 12.0% |
| Kingston, IL | 1,183 | 42 | 16.0% |
| Queen Anne, MD | 1,183 | 36 | 28.0% |
| North Collins, NY | 1,183 | 39 | 22.0% |
| Chesapeake, OH | 1,183 | 42 | 16.0% |
| Granby, MA | 1,183 | 40 | 20.0% |
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