Any weather forecast, of its nature, is a very general description of the expected weather pattern. The national or regional forecast you get from radio or TV must be interpreted with due regard for the lie of the local land.
The wind, for example, responds in a characteristic way to the topography of each locality. This is largely due to the fact that air dislikes passing over obstacles, and much prefers to go around them if it can. A long range of hills, therefore, tends to deflect the wind so it blows parallel to it, even if the hills are not very high. This may lead to a wind direction at a particular spot very different from the forecaster's prediction.
This same tendency for air to circumnavigate obstacles in its path affects the wind's strength. Air approaching a gap in an otherwise solid range of hills prefers to squeeze through the opening rather than to rise over the high ground. This can lead to a much stronger wind than elsewhere in the vicinity, a so-called ravine wind.
Likewise in the case of temperature, local factors may cause it to be colder or warmer than the forecast might lead you to expect. The most obvious way in which the temperature can differ from place to place is with altitude. The average rate of decrease in temperature with height is about 2 Celsius per 1,000 ft, which explains why you sometimes get snow on high ground, when temperatures are forecast generally to be around 6C or 7C.
Another local factor, particularly important at this time of year, which may cause the temperature to be lower than elsewhere in the vicinity, is the katabatic effect. On a winter night with clear skies, outgoing radiation from the Earth causes the ground to become very cold.
The temperature of the air in immediate contact with this surface quickly falls well below that of the air above it in the atmosphere. If the ground has a slope to it, the colder, and therefore heavier, air slides down the incline, resulting in a pool of cold air at the base of the slope.
The force of the air sliding down a hill like this on a frosty night can often be felt as a fresh cold breeze, a so-called katabatic wind. With undulating countryside, the katabatic effect results in pools of cold air in the valleys on clear nights, and temperatures quite a few degrees lower than you might otherwise expect. Frost is common in these valleys, which are often well known locally as "frost hollows".