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Saint John climate by month
What the weather is like
Saint John has a warm-summer humid continental climate (Köppen Dfb): warm summers, cold winters and precipitation in every season.
The warmest month is August, when afternoons average 20° and nights 12°. January is the coolest month, with highs of -1° and lows of -10°. The difference between the warmest and the coolest month is about 22°, a large swing typical of continental interiors.
About 1,339 mm of precipitation falls in an average year. July is the wettest month (94 mm, 15 wet days) and September the driest (109 mm, 9 wet days). Cloud cover ranges from 38% in September to 47% in April.
The sea reaches about 14° in August. Sea temperatures lag the air by a month or two, so late summer is usually warmer for swimming than early summer.
Compared with Ottawa, the capital, Saint John is 5.3° cooler on a August afternoon and receives more precipitation over the year.
Year in figures
- Hottest afternoons
- 20° · August
- Coldest nights
- -10° · January
- Wettest month
- July
- Driest month
- September
- Clearest skies
- September · 38% cloud
- Warmest sea
- 14° · August
- Longest day
- 15 h 38 min
- Shortest day
- 8 h 46 min
Twelve months at a glance
Temperature and precipitation
Daily high/low range bars, monthly precipitation columns, sea temperature lineTemperature curve
Average high, low and seaDaylight
Hours between sunrise and sunset on the 15th of each monthClimate normals month by month
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Average high | -1° | 0° | 3° | 8° | 13° | 17° | 20° | 20° | 18° | 13° | 8° | 2° |
| Average low | -10° | -9° | -5° | 1° | 5° | 9° | 12° | 12° | 10° | 5° | 1° | -5° |
| Precipitation | 111 mm | 101 mm | 108 mm | 105 mm | 111 mm | 107 mm | 94 mm | 94 mm | 109 mm | 124 mm | 143 mm | 132 mm |
| Wet days (≥1 mm) | 12.5 | 10.7 | 12.7 | 12.5 | 12 | 14 | 15.2 | 13 | 8.8 | 10 | 11.3 | 14 |
| Cloud cover | 45% | 45% | 45% | 47% | 46% | 46% | 45% | 40% | 38% | 40% | 47% | 46% |
| Sea temperature | 5° | 3° | 2° | 3° | 6° | 9° | 13° | 14° | 13° | 12° | 10° | 7° |
| Daylight | 9h 07 | 10h 25 | 11h 52 | 13h 30 | 14h 52 | 15h 38 | 15h 19 | 14h 07 | 12h 34 | 11h 00 | 9h 33 | 8h 46 |
| Month score | 22 | 27 | 22 | 21 | 37 | 56 | 61 | 65 | 76 | 47 | 24 | 18 |