A typical Los Angeles night is now warmer than 65% of the nights people had at that time of year in 1951–1980.

Each spiral is one station: January at the top, the year running clockwise, and the distance from the centre the daily high, 15-day means on the station's own scale. One ring per year — the palest from the 1940s and 50s, the darkest the last few years, the bold one the year on the slider. The shaded rings are the middle 80% and middle 50% of the station's baseline years for each date and the dashed ring their median: a bold ring outside the shading is warmer than almost any baseline year at that date. The two badges are the station's scores — where a typical day (red, top right) and a typical night (blue, top left) of its last ten complete years fall among the baseline's for the same date; 50 would mean no change, 70 that a typical night now is warmer than 70% of the baseline's. Baseline is 1951–1980; † marks a station without that record, scored against its own earliest 20 complete years. Click a spiral for the station.

Press play to watch the rings accumulate; drag the year to pick out one ring (drawn dark) against everything before it.

Two numbers per station

The same idea averaged over each station's last ten complete years: where a typical night and a typical day at each station now fall among 1951–1980 readings for the same time of year.

Press play, or drag the year. Each pill is one station's count for that year (hover for the name); “≥” means the year is incomplete there and the count is a lower bound; stations with no data that year are hidden. Colors use one scale for every year. All LA stations, as a table →

What it feels like: nights that never cool below 70°F, days that reach 95°F

Percentiles are the fair comparison; these fixed thresholds are the lived experience — and a 70°F night means something different at the beach than in the valley. One row per station, longest records first: its own trend over its own complete years, with a 90% range. Filled dots are trends clearly different from zero.

Why nights and days differ: the trend at each station

For every station, the trend in its June–August mean daily low (filled) against its mean daily high (hollow), over the station's own complete years. Nights lead at most stations; at a few inland and coastal-military sites, days do.

This summer so far

Average daily high from June 1 through each station's latest reading, ranked against every other summer at that station over the same dates.

Nights at LAX whose low never fell below 70°F. Dark steps are decade averages.

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Los Angeles as a whole — a model, not an average

Stations come and go, so a plain average of whatever stations exist each year would mostly track the network. These two charts come from a model that treats each station's missing years as unknowns and estimates what the typical station would have counted had every station reported every year, with a 90% band (how, and how well it predicts held-out data).

The same shift, at the beach, in the valleys, on the mountain, in the desert

Nights per year at or above 70°F, averaged by decade, at every station.

Each dot is the average per year over a decade (complete years only). * = current decade so far. Panels sorted by change; same vertical scale everywhere.

Hot days: up inland, flat at the coast

Days per year at or above 95°F. The marine layer keeps coastal afternoons in check; the valleys and the desert get the extra heat.

Each dot is the average per year over a decade (complete years only). * = current decade so far. Panels sorted by change; same vertical scale everywhere.

Every summer at LAX since 1940

One row per summer, newest at the top; one square per day, colored by that day's high. Look for the dark streaks.

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LAX's nights, as stripes

Nights have warmed about 0.4°F per decade at LAX since 1951 (days: 0.1°F per decade).

Heat waves per summer, year by year

The front-page heat waves, counted per complete summer at each station with a baseline. The count swings from year to year and decade to decade — the 2000s were quiet everywhere, the 1950s busy at the coast — but at the coast and in the basin the recent average sits where the mid-century one did; inland stations run about one extra heat wave a year.

The whole country

The same records exist for every long-running station in the United States — 1,971 of them with 50+ years of daily readings. Open the national map →