Grantham Weather Forecast
- 66
- 91
Thunderstorms
- 59
- 84
Chance Rain Showers
- 55
- 82
Mostly Sunny
- 62
- 86
Mostly Sunny
- 58
- 85
Chance Rain Showers
- 52
- 75
Partly Sunny
Today 13 Aug Sullivan
Mostly sunny. Patchy fog this morning. Scattered Showers and Thunderstorms this afternoon. Some Thunderstorms may produce gusty Winds this afternoon. Hot with Highs around 90. Light and variable Winds. Chance of rain 50 percent. Heat index Values in the mid 90s this afternoon.
Tonight 13 Aug Sullivan
Scattered Thunderstorms in the evening. Mostly cloudy with scattered Showers. Patchy fog after midnight. Some Thunderstorms may produce gusty Winds in the evening. Humid with Lows in the upper 60s. Light and variable Winds. Chance of rain 40 percent.
Grantham Temperature Statistics
August Temperature
Lebanon Municipal Airport (12.4 miles)
Lowest 2 August, 2025
46.7 °FAverage August
71.9 °FHighest 11 August, 2025
93 °F
Climate (2020–Present)
Lebanon Municipal Airport (12.4 miles)
Average Low 2020–2025
38.2 °FAverage 2020–2025
48.8 °FAverage High 2020–2025
59.8 °F