Definitions of codes

Help to understand the codes we use to describe the weather.

Weather types

NANot available
0Clear night
1Sunny day
2Partly cloudy (night)
3Partly cloudy (day)
4Not used
5Mist
6Fog
7Cloudy
8Overcast
9Light rain shower (night)
10Light rain shower (day)
11Drizzle
12Light rain
13Heavy rain shower (night)
14Heavy rain shower (day)
15Heavy rain
16Sleet shower (night)
17Sleet shower (day)
18Sleet
19Hail shower (night)
20Hail shower (day)
21Hail
22Light snow shower (night)
23Light snow shower (day)
24Light snow
25Heavy snow shower (night)
26Heavy snow shower (day)
27Heavy snow
28Thunder shower (night)
29Thunder shower (day)
30Thunder

Visibility

UN Unknown
VP Very poor - Less than 1km
PO Poor - Between 1-4 km
MO Moderate - Between 4-10 km
GO Good - Between 10-20 km
VG Very good - Between 20-40 km
EX Excellent - More than 40 km

UV Index

The strength of the sun's ultraviolet (UV) radiation is expressed as a 'Solar UV Index', a system developed by the World Health Organization. These Met Office forecasts include the effects of:

  • the position of the sun in the sky;
  • forecast cloud cover;
  • ozone amounts in the stratosphere.

The solar index does not exceed 8 in the UK (8 is rare; 7 may occur on exceptional days, mostly in the two weeks around the summer solstice). Indices of 9 and 10 are common in the Mediterranean area.

The UV Index can take the following values:

1-2 Low exposure. No protection required. You can safely stay outside
3-5 Moderate exposure. Seek shade during midday hours, cover up and wear sunscreen
6-7 High exposure. Seek shade during midday hours, cover up and wear sunscreen
8-10 Very high. Avoid being outside during midday hours. Shirt, sunscreen and hat are essential
11 or over Extreme. Avoid being outside during midday hours. Shirt, sunscreen and hat essential.

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