Our data sources

Sharing accurate weather and climate information is at the heart of what we do. We only work with the very best sources to fill our pages with useful data, whether we're talking about average temperatures, the weather forecast, where to go in a given month or snow cover.

Here, we aim to clearly show you where we gather our data from, how we interpret it, and how we share it with you, our readers.

  1. Climate guides
  2. Holiday weather overview
  3. Best time to go
  4. Monthly weather information
  5. Current weather
  6. Weather forecasts
  7. Snow reports
  8. Tropical storms

1. Climate guides

Mean monthly values for the following weather parameters were computed by the Climatic Research Unit of the University of East Anglia in a high resolution global gridded dataset (CRU CL v. 2.0).

It is based on 30 years of meteorological observations from 1961 to 1990. The resolution of the grid is 10 minutes, which equates to an area about 18 x 18 km at the equator. This applies to the following data we share across our climate guides:

  • Average maximum daytime temperature for each month
  • Average minimum daytime temperature for each month
  • Average daily hours of sunshine for each month
  • Average number of days with some rainfall for each month
  • Average amount of rainfall for each month

Additional parameters

The following weather parameters are also shown in our climate guides.

Heat & humidity

When we talk about heat and humidity, we are referring to the average level of discomfort caused by heat and humidity for each month. This index gives an idea of how high levels of humidity can affect how the weather feels when temperatures are also high.

It is derived from a formula based on research by Professor Richard de Dear at the University of Sydney in Australia on Thermal Comfort.

The formula can predict the level of discomfort caused by a combination of high temperature and high vapour pressure, a measure of the amount of water vapour in the air.

Values for average monthly vapour pressure are included in the University of East Anglia Climatic Research Unit's gridded climatology of 1961-1990 (CRU CL v. 2.0).

More about heat & humidity >>

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Sea temperature

The sea temperature figures shown across Weather2Travel.com display the average sea temperature for each month in a given destination.

These sea surface temperatures come from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) project produced by the UK Met Office.

The values displayed are monthly averages computed from 23 years of satellite observations covering the years from 1985 to 2007.

The gridded dataset is provided courtesy of Copernicus Marine Environment Monitoring Service. The resolution of the grid is three minutes, which equates to an area about 6 x 6 km at the equator.

More about sea temperature >>

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UV maximum levels

The figures we display for the UV maximum levels show the average maximum daytime UV radiation for each month in a given destination.

The World Health Organisation, United Nations Environment Programme and the World Meteorological Organisation have standardised the scale and method of calculating UV indexes.

Weather2Travel.com displays monthly UV index values from TEMIS, which are produced by the Royal Netherlands Meteorological Institute (KNMI) from information gathered by satellite between August 1995 and May 2003 (eight years of data).

Known as a clear-sky UV index, the index shows the level of UV holidaymakers can expect when the sky is clear of clouds and the sun is at its strongest around midday.

The resolution of the gridded data is half a degree which equates to an area about 50 x 50 km at the equator.

More about UV levels >>

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Daylight hours

The figure for daylight hours shown across Weather2Travel.com is the average number of hours of daylight per day in every month.

Sunrise and sunset times for each day of the month are calculated to a high level of accuracy based on some well established but complex astronomical formulae.

The total number of daylight hours is then divided by the number of days in the month and rounded to the nearest hour.

For precise sunrise and sunset times for specific days, see our 'weather by month' pages.

More about daylight >>

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2. Holiday weather overview

The information showing what the weather is usually like in each month comes from the Climatic Research Unit of the University of East Anglia's high resolution global gridded dataset of mean monthly values covering 30 years from 1961 to 1990, known as CRU CL v. 2.0.

  • Average maximum daytime temperature for each month
  • Average minimum daytime temperature for each month
  • Average daily hours of sunshine for each month

For comparison the information about what the weather is like now comes from today's weather forecast provided by the Swiss meteorological agency MeteoBlue.

  • Expected maximum daytime temperature for today
  • Expected prevailing weather conditions for today
  • Expected number of hours of sunshine for today

Explore holiday weather >>

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3. Best time to go

The daytime maximum temperature, sunshine hours, monthly rainfall, days with some rain, and heat and humidity used to compute the star ratings in our 'best time to go' guide come from the Climatic Research Unit of the University of East Anglia's high resolution global gridded dataset, based on 30 years of meteorological observations from 1961 to 1990.

The sea temperature data is from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) project produced by the UK Met Office.

  • Average maximum daytime temperature for each month
  • Average daily hours of sunshine for each month
  • Average number of days with some rainfall for each month
  • Average amount of rainfall for each month
  • Average level of discomfort caused by heat and humidity for each month
  • Average sea temperature for each month

Find best time to go >>

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4. Monthly weather information

The daytime maximum temperature, sunshine hours, days with some rainfall, minimum nighttime temperature, heat and humidity and monthly rainfall in 'monthly weather information' come from the Climatic Research Unit of the University of East Anglia's high resolution global gridded dataset, based on 30 years of meteorological observations from 1961 to 1990.

The maximum UV radiation is from TEMIS produced by the Royal Netherlands Meteorological Institute (KNMI) based on eight years of data.

Meanwhile, sea temperatures are from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) project produced by the UK Met Office, based on 23 years of observations.

The number of hours of daylight are calculated by a complex series of astronomical formulae.

  • Average maximum daytime temperature for each month
  • Average daily hours of sunshine for each month
  • Average number of days with some rainfall for each month
  • Average minimum nighttime temperature for each month
  • Average number of hours of daylight per day in every month
  • Average level of discomfort caused by heat and humidity for each month
  • Average amount of rainfall for each month
  • Average maximum daytime UV radiation for each month
  • Average sea temperature for each month

Explore weather by month:

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

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5. Current weather

Weather2Travel.com's source of current weather are METARS (aviation routine weather reports) that are issued frequently (usually every hour) by airports and airfields around the world.

The reports are re-distributed in real time by the United States meteorological agency (NOAA). We check these every 15 minutes and publish the updates as they arrive.

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6. Weather forecasts

Weather2Travel.com's weather forecasts are supplied by MeteoBlue, a meteorological service provider based in Switzerland offering, among other things, weather forecasts for every part of the world.

Originally part of the University of Basel, it was spun off as a private company in 2006. Weather2Travel.com receives updated forecasts for all destinations every 12 hours.

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7. Snow reports

Weather2Travel.com's snow reports are derived from a dataset known as 'Jasmes Northern Hemisphere snow cover extent', produced by the Japanese Space Agency from resampled AVHRR and MODIS radiance data provided by NOAA and NASA.

The original data, in daily, weekly and monthly formats, covers the period from 1978 to 2015 at 5 km resolution. The average values shown in the Weather2Travel.com's reports are based on the most recent fifteen years of weekly data from 2000 to 2015.

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8. Tropical storms

Weather2Travel.com's information on tropical storms is processed from data provided by NOAA, the United States meteorological agency.

Its International Best Track Archive for Climate Stewardship (IBTrACS) shows the position and intensity every six hours of all tropical storms going back over 100 years.

Weather2Travel.com performed spatial analysis on the data for the period January 1951 to December 2010 (60 years) to produce values for the average number of storm affected days per month when a storm comes within 350 km of each destination.

The results show the percentage of days in the month that are normally affected by tropical storms.

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More about our weather parameters

You can find out more about individual weather parameters below:

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