Based on data reported by over 4,000 weather stations
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
| Average temp. (°F) | 30.3 | 30.6 | 36.7 | 44.9 | 54.1 | 62.9 | 69.2 | 68.7 | 62.8 | 53.1 | 44.7 | 35.7 |
| High temperature (°F) | 37.5 | 37.7 | 43.2 | 51.0 | 60.3 | 69.4 | 76.0 | 75.3 | 69.4 | 60.0 | 51.0 | 42.6 |
| Low temperature (°F) | 23.0 | 23.5 | 30.1 | 38.6 | 47.8 | 56.3 | 62.4 | 62.0 | 56.3 | 46.1 | 38.3 | 28.8 |
| Precipitation (in) | 4.1 | 3.7 | 4.1 | 3.9 | 3.5 | 3.3 | 3.2 | 3.4 | 3.7 | 4.0 | 3.9 | 4.4 |
Based on data reported by main weather stations
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
| Days with precip. | 12 | 10 | 12 | 11 | 12 | 11 | 10 | 10 | 9 | 9 | 11 | 12 |
| Wind speed (mph) | 14.0 | 14.2 | 14.4 | 13.9 | 12.5 | 11.8 | 11.2 | 10.9 | 11.4 | 12.3 | 13.2 | 13.6 |
| Morning humidity (%) | 73 | 72 | 73 | 70 | 73 | 76 | 77 | 80 | 81 | 79 | 77 | 73 |
| Afternoon humidity (%) | 59 | 56 | 56 | 52 | 55 | 57 | 56 | 58 | 59 | 56 | 59 | 59 |
| Sunshine (%) | 51 | 54 | 54 | 54 | 56 | 59 | 61 | 61 | 60 | 58 | 49 | 50 |
| Days clear of clouds | 9 | 8 | 8 | 7 | 6 | 7 | 7 | 8 | 9 | 11 | 8 | 8 |
| Partly cloudy days | 7 | 7 | 8 | 8 | 10 | 10 | 12 | 11 | 8 | 8 | 7 | 8 |
| Cloudy days | 15 | 13 | 15 | 15 | 15 | 13 | 12 | 12 | 12 | 12 | 15 | 15 |
| Snowfall (in) | 12.8 | 12.4 | 9.2 | 1.7 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 1.8 | 8.6 |
Average time Harwich Port High Tide behind Boston: 52 minutes
Average time Harwich Port Low Tide behind Boston: 25 minutes
Average time Round Cove High Tide behind Boston: 2 hours 28 minutes
Average time Round Cove Low Tide behind Boston: 3 hours 25 minutes
Average time Round Cove High Tide behind Harwich Port: 1 hours 35 minutes
Average time Round Cove Low Tide behind Harwich Port: 3 hours 0 minutes