We use research datasets and official information to show how temperature and rainfall have changed. Here is what the figures mean, in simple words.
Historical climate data, not today’s weather forecast
Four things to know
Temperature
Most figures are the average of day and night, measured 2 metres above the ground. Daily highs and lows are typical values, not records.
Rainfall
Monthly totals in mm, from a model. They follow wet and dry years but miss heavy downpours, so they carry low confidence.
Change from usual
We compare each month with the 1991 to 2020 average for the same calendar month at the same place.
Estimates and records
Model estimates, thermometer records and the 1991 to 2020 usual are kept apart and labelled. Official records are kept on the Records page, apart from our estimates.
Sources used and referenced
Only sources that the data now on the site really uses are listed.
Our own figures: the averages, changes from usual and CSV files that HowToSurvive.in calculates from these sources are shared under CC BY 4.0 (opens in a new tab), with credit to HowToSurvive.in and to the sources below. The source data keeps the terms of its providers.
ERA5 monthly averaged data on single levels, 1940 to present
Copernicus Climate Change Service (C3S), ECMWF
Monthly average temperature and monthly rainfall for the world, India, states and cities, and the colours of the maps. A past-weather record rebuilt by a computer model from millions of real measurements.
Licence: CC BY 4.0. We average it over areas, re-base it to 1991 to 2020 and round it.
Generated using Copernicus Climate Change Service information (2026). Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.
ERA5 hourly data on single levels, 1940 to present
Copernicus Climate Change Service (C3S), ECMWF
Typical daily highs and lows, worked out from hourly model data and, where a thermometer exists nearby, adjusted to it.
Licence: CC BY 4.0. Model estimates, not thermometer readings.
Generated using Copernicus Climate Change Service information (2026). Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.
NASA GISS Surface Temperature Analysis (GISTEMP) version 4
NASA Goddard Institute for Space Studies
A cross-check of our world temperature against NASA’s own world record. The yearly figures agree closely from 1950 to 2025.
Licence: NASA open data; citation and acknowledgment requested. GISTEMP is published against 1951 to 1980; we re-base it to 1991 to 2020 for the check.
NASA's Goddard Institute for Space Studies (GISS), GISTEMP v4.
India Meteorological Department (IMD) published figures
India Meteorological Department
India’s monsoon rain as a percentage of normal, and a check on the India temperature series. Only numbers that IMD prints in its own reports are used, with the document named. The Records page also copies station records from IMD documents, each named there with its station, date and link.
Licence: Not a data licence: figures as printed by IMD, no raw data files copied. The documents used are listed under the monsoon figures in the explorer’s “How we know” section.
Source: India Meteorological Department. IMD has not endorsed this page.
NOAA Global Historical Climatology Network daily (GHCN-Daily)
NOAA National Centers for Environmental Information
Weather-station daily highs and lows, used to check the model and, for cities with a station within 25 km, shown as a separate thermometer block.
Licence: NOAA open data (the data page gives no separate licence sentence). Stations have gaps and are not homogenised; years with too few days are left out.
Weather-station records: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily).
Daily highs for the hot-day estimates (hottest day since 1981, days at or above 35 and 40 degrees) shown for some cities, adjusted to a nearby thermometer where one exists. Estimates, not records.
Licence: NASA open data service. Squares about 50 km wide. Daily rain from this source is no longer shown.
Typical daily highs and extreme temperature records are different measures. A typical daytime high is never “the highest ever”.
“Warmer than usual” means warmer than a reference period.
We use 1991 to 2020 for every comparison, month by month, at the same place.
Rainfall can vary within a city.
The gridded estimate is for a square about 28 km wide and may miss the heaviest local downpours.
More definitions
Average temperature
Degrees Celsius of the air 2 metres above the ground, averaged over the whole day and night. It is lower than the afternoon highs that news reports quote, and higher than the early-morning lows.
Typical daytime high and night-time low
The average of the daily highs (or daily lows) over a month or a year. These are estimates from model data, adjusted to a nearby thermometer where one exists.
Change from usual
The value for a month minus the 1991 to 2020 average of that calendar month. A yearly change is the average of the twelve monthly changes, and only complete years of twelve months are used for yearly figures, ranks and trends.
Trend per decade
The slope of a straight line through the yearly changes, multiplied by ten, with a 95 per cent range. A short or noisy record gives a wide range, so a trend is shown with a confidence label.
Hot-day estimates
For some cities: the hottest day of a year in the data (from 1981) and the number of days at or above 35 and 40 degrees. They are estimates from daily model data, adjusted to a nearby thermometer where one exists, and carry an error that the page states. The count of days has a larger error than the hottest day. They are not records.
Rainfall in mm
The monthly total from the same model record, for a square about 28 km wide (cities, states and India). It is a rough estimate with low confidence.
Monsoon rain as a percentage of normal
Figures published by IMD in its own reports, measured by rain gauges, for the whole of India. IMD has not endorsed this page.
What we will always show
The place and the years the figure covers.
The data source, and how recently it was updated.
Units, how it was calculated and what it cannot tell you.
A clear “Not available” when we do not have a figure.
Common questions
Can past climate data tell me next week’s weather?
No. These pages show what has already happened, as monthly and yearly averages. For today’s weather and warnings, use the India Meteorological Department (IMD) forecasts and warnings.
Why does the figure for my town differ from a weather station?
A town is shown as the model grid square nearest its centre, about 28 km wide. The model smooths out hills, the coast and the heat of a built-up city, so it can differ from a thermometer by about 0.5 to 1 degree, and more in hill, coastal and high places.
What does “usual” mean?
The average of 1991 to 2020 for the same calendar month at the same place. “2 degrees above usual” means 2 degrees warmer than that average for that month.
Why is rainfall called low confidence?
Monthly rain here comes from a computer model, and a model smooths out downpours. It follows wet and dry years reasonably, but it is a rough estimate. We do not show heavy-rain-day counts, the wettest day or dry spells, because they have not been checked against rain gauges.
Is a “hottest day” on your pages an all-time record?
No. It is the hottest day in the data period named next to it, for example since 1981. It is a model estimate, adjusted to a nearby thermometer where one exists, and not an all-time record for the city.
Why does India start in 1954?
The model reads about 0.9 degrees too cold over India in 1950 to 1953 when checked against weather stations. So India figures start in 1954. The earlier years can be switched on in the explorer, with a warning.
Can I use these figures in a report or school project?
Yes, but please say they are model estimates averaged by HowToSurvive.in and name the original sources listed above. For the underlying data, follow each source’s own terms.
Every number on the Climate pages belongs to one of three kinds, and we try to say which.
Three kinds of figure
Kind
What it is
Can it be called a record?
Model estimate
A value from a reanalysis (a past-weather record rebuilt by a computer model) for a grid square. Most of what you see.
No. It smooths hills, coast and city heat.
Thermometer record
A reading from a weather station, shown only where a station is within 25 km and has enough years.
Only as “the highest in this station’s data since the year shown”, never “of all time”.
Usual (1991 to 2020)
The reference average that other figures are compared with.
No. It is an average, not an extreme.
Official records need a verified station, date, unit and source. The Records page lists only those we could check in IMD and WMO documents, and we never compare a record with a grid estimate.
How far off can the figures be?
Figures are computer-model estimates for the area around a place. They can differ from a weather station by 1 to 3 °C and rainfall by 20 to 50 percent, more in hills, on coasts and in Ladakh.
The national India series is also model-based (the ERA5 average of all land squares inside India). Its average level, about 23.9 °C for 1991 to 2020, is roughly 1.3 °C below the all-India mean temperature that the India Meteorological Department publishes, because the squares include the cold high Himalaya and the model reads lower than thermometers on average. Year-to-year changes and the long-term rise follow the published national anomalies closely, so the trend wording on this site is unchanged; use the level as a model figure, not as IMD’s own number.
The 1991 to 2020 usual
The World Meteorological Organization’s current standard period for “normal” climate is 1991 to 2020. We use it for every comparison, calendar month by calendar month. NASA’s world record is published against 1951 to 1980; for the cross-check we re-base it to 1991 to 2020 ourselves.
Early figures and the 1954 start for India
The latest three months come from an early release of the model and can change slightly when the final version replaces them (this applies from July 2026 now). They are marked “early” in the explorer.
For India, the model reads about 0.9 degrees too cold in 1950 to 1953 when checked against 73 weather stations, so India figures start in 1954. Single months from 1954 to 1956 can still be off by 1.5 degrees or more. The earlier years can be switched on in the explorer.
A few single months are flagged by hand where we know the model is off, for example Delhi in May 1956.
How fine is the picture?
A city is the model grid square nearest its centre, about 28 km wide. A state is the average of the squares inside it, so small states and islands rest on few squares.
The India temperature map uses squares about 55 km wide and the India rain map squares about 110 km wide. Outside India both maps use squares about 222 km wide, so they show broad patterns, not single towns.
The map shows grid squares only. Boundaries are not drawn, and the squares are not a political map.
Our checks against weather stations cover India only. Treat places elsewhere as model estimates.
The data covers 181 places: the world, India, 36 states and union territories and 143 cities.
Rainfall and its limits
The model’s rain is a smooth picture. At the three cities we checked, it counted 2 to 9 times fewer heavy-rain days than rain gauges. For that reason this site does not show heavy-rain-day counts, the wettest day or dry spells. They will return only after daily rain has been checked against gauges. Monthly totals and the monsoon figures published by IMD remain, with their labels.
What is not available yet
We would rather write “Not available” than guess. Not shown at present: heatwave days, warm nights, heat index, official records for most states and places, heavy-rain-day counts, dry spells, and district-level figures (the data is by state and city). Climate figures here are history. They are never a weather alert; for warnings use IMD and the National Disaster Management Authority.
Calculation examples
Change from usual, real figures. India averaged 23.7 °C in 2025. The usual (1991 to 2020 average) is 23.6 °C. So the change is 23.7 − 23.6 = +0.1 °C (model estimate, rounded).
Typical daytime high, simple numbers (not a real place). If the daily highs of a 30-day month add up to 1,050 degrees, the typical daytime high of that month is 1,050 ÷ 30 = 35.0 °C. The hottest single day of that month may be several degrees more, which is why a typical high is not a record.
Change log
4 November 2026. Records and rankings page added. It lists only records that we opened and checked in IMD and WMO documents, and keeps our own model rankings apart. Everything we could not verify says “Not available”.
4 November 2026. Data sources and methods and Climate safety pages added. Heavy-rain-day, very-heavy-rain-day, wettest-day and dry-spell figures removed from the Extreme days section, because daily rain from the model has not been checked against rain gauges. Hot-day estimates stay, labelled as estimates. The line “Next update about …” was replaced by “Refreshed about every three months”.
5 November 2026. Data package built, with data to September 2026.
Data to September 2026. Figures from July 2026 onwards are early and can change a little. Data package built 5 November 2026. Refreshed about every three months.
