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    weather temperature

    how do the local weather forecast take measurements for temperature that they use or predict as like today and some other days outside temperature is in minus as water freezers on ground and car windscreens but they show it as 3 or maybe even upto 6 degrees if they are correct than how does the water freeze doesn't make sense. anyone know the answer to this.

    9 Comments

    Google it.

    Wind

    The weather station location is a major factor as that is where the info is collected and based on so its only a general guide for the area. Forecast is based on air temperature not ground temperature. The ground temperature can vary due to its composite . It can be slower to warm up to air temperature and therefore freeze water. Other factors such as wind and air pressure are involved.

    Find a local weather station as folks have them in the back garden and link to net. Also airports have them. I'm lucky as have both near me so I have 1 bookmarked. Just looked. It's - 1.5c. BBC weather app says it's 0c

    it's about air pressure and how it squeezes the jet stream as to if we get Atlantic air which is mild and wet or continental air which is colder at this time of year. if there is high presure sitting over us we will have frosty clear sky's.

    brendanhickey

    it's about air pressure and how it squeezes the jet stream as to if we … it's about air pressure and how it squeezes the jet stream as to if we get Atlantic air which is mild and wet or continental air which is colder at this time of year. if there is high presure sitting over us we will have frosty clear sky's.



    ​Thats not what the OP asked. They're asking how moisture in the air freezes when the temperature stated by forecasters is higher than 0°C.

    It's called a weather forecast i.e. A prediction based on data
    A prediction/estimate

    The difference is between 'air frost' and 'ground frost'.
    If you have an air temp below freezing, water molecules in the air (which are invisible) will freeze and deposit themselves on what ever is around as visible frost.

    Ground Frost will occur when the air temp is above freezing but the ground is cooling more quickly than the air above it. The ground does this at night because it radiates back to space the heating effect of the sun, which the earth stores, during daylight hours.
    Because of this rapid loss of heat, the surface of the ground can be a few degrees cooler than the surrounding air, so frost can form on grass or freeze over shallow puddles of water.

    This effect is most noticeable on a clear cloudless night as the lack of cloud cover allows the maximum heat radiation from the earth to escape. With cloud cover some of the escaping radiation is reflected back down to earth, known as the greenhouse effect.
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