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Season 1991

Every heat event the pipeline tracked between 1991-05-01 and 1991-09-30, with how each one grew, peaked and moved. Anomalies are against the 1991–2020 baseline.

Season at a glance

Events tracked
15
Total heat burden
20.16 Mkm²·days
Longest
16days (#5)
Hottest
+14.4°C (#5)
With a heat dome
7of 15 events

A heat dome is the stricter object: a tracked heat event with a closed 500 hPa anticyclone whose influence cap overlies it, after Loikith et al. (2026). Most heatwaves are not domes, so the label is a finding and not a synonym.

ERA5 daily maximum 2 m temperature over land, against the 1991–2020 climatology (p90 in a centred 15-day window). A heatwave cell is Tx above p90 on at least 3 consecutive days.

When the events ran

MayJunJulAugSep#19 d · +12.1 °C#27 d · +8.6 °C#34 d · +8.4 °C#44 d · +9.7 °C#516 d · +14.4 °C#67 d · +13.8 °C#713 d · +13.4 °C#89 d · +11.1 °C#911 d · +12.1 °C#107 d · +12.9 °C#1114 d · +8.6 °C#126 d · +10.8 °C#136 d · +9.8 °C#149 d · +11.6 °C#154 d · +11.0 °C1991-05-01 → 1991-09-30; bar colour is peak anomaly (+4 to +16 °C); filled dot = heat dome, hollow = no overlying high

Overlapping bars are concurrent events in different places, not one event counted twice: each is a separately labelled cluster of contiguous heatwave cells.

How each event evolved

Event #5 — 1991-06-22 → 1991-07-07 16 daysheat dome · 10/16 d · Z500 +240 m

peak 877k km² on 1991-07-01 · max +14.4 °C · mean +8.5 °C · burden 5.98 M km²·d · drift 1383 km (53.5 N 44.4 E → 41.1 N 44.7 E)

877kkm²+14.4+0.0 °C1991-06-221991-07-07peak 1991-07-01centroid drift · 16.9° box

Event #6 — 1991-07-03 → 1991-07-09 7 daysheat dome · 7/7 d · Z500 +326 m

peak 413k km² on 1991-07-07 · max +13.8 °C · mean +8.6 °C · burden 2.12 M km²·d · drift 293 km (60.1 N 8.8 E → 61.3 N 13.6 E)

413kkm²+13.8+0.0 °C1991-07-031991-07-09peak 1991-07-07centroid drift · 2.9° box

Event #14 — 1991-09-14 → 1991-09-22 9 daysheat dome · 6/9 d · Z500 +189 m

peak 377k km² on 1991-09-17 · max +11.6 °C · mean +7.2 °C · burden 1.72 M km²·d · drift 459 km (40.0 N -8.3 E → 42.0 N -3.5 E)

377kkm²+11.6+0.0 °C1991-09-141991-09-22peak 1991-09-17centroid drift · 4.5° box

Event #7 — 1991-07-09 → 1991-07-21 13 dayshigh on 6/13 d only

peak 240k km² on 1991-07-17 · max +13.4 °C · mean +6.5 °C · burden 1.45 M km²·d · drift 472 km (39.5 N -4.5 E → 42.8 N -8.1 E)

240kkm²+13.4+0.0 °C1991-07-091991-07-21peak 1991-07-17centroid drift · 5.0° box

Event #10 — 1991-08-24 → 1991-08-30 7 dayshigh on 2/7 d only

peak 281k km² on 1991-08-27 · max +12.9 °C · mean +7.1 °C · burden 1.34 M km²·d · drift 148 km (43.3 N -0.8 E → 44.6 N -0.5 E)

281kkm²+12.9+0.0 °C1991-08-241991-08-30peak 1991-08-27centroid drift · 1.6° box

Event #11 — 1991-08-25 → 1991-09-07 14 daysheat dome · 10/14 d · Z500 +354 m

peak 164k km² on 1991-08-31 · max +8.6 °C · mean +5.0 °C · burden 1.19 M km²·d · drift 651 km (50.7 N -4.3 E → 56.5 N -4.4 E)

164kkm²+8.6+0.0 °C1991-08-251991-09-07peak 1991-08-31centroid drift · 7.3° box

Event #12 — 1991-08-30 → 1991-09-04 6 dayshigh on 3/6 d only

peak 271k km² on 1991-09-02 · max +10.8 °C · mean +5.8 °C · burden 1.10 M km²·d · drift 148 km (59.9 N 11.1 E → 58.6 N 10.7 E)

271kkm²+10.8+0.0 °C1991-08-301991-09-04peak 1991-09-02centroid drift · 2.2° box

Event #9 — 1991-08-10 → 1991-08-20 11 daysheat dome · 6/11 d · Z500 +128 m

peak 235k km² on 1991-08-16 · max +12.1 °C · mean +6.4 °C · burden 1.08 M km²·d · drift 264 km (40.9 N -8.9 E → 42.8 N -6.9 E)

235kkm²+12.1+0.0 °C1991-08-101991-08-20peak 1991-08-16centroid drift · 4.2° box

Event #8 — 1991-07-28 → 1991-08-05 9 daysheat dome · 7/9 d · Z500 +193 m

peak 205k km² on 1991-07-31 · max +11.1 °C · mean +7.0 °C · burden 852k km²·d · drift 483 km (62.1 N 12.1 E → 66.2 N 15.6 E)

205kkm²+11.1+0.0 °C1991-07-281991-08-05peak 1991-07-31centroid drift · 5.8° box

Event #13 — 1991-08-31 → 1991-09-05 6 daysno overlying high

peak 223k km² on 1991-09-03 · max +9.8 °C · mean +7.1 °C · burden 832k km²·d · drift 327 km (51.6 N 5.7 E → 48.9 N 7.2 E)

223kkm²+9.8+0.0 °C1991-08-311991-09-05peak 1991-09-03centroid drift · 3.5° box

Event #1 — 1991-05-20 → 1991-05-28 9 daysno overlying high

peak 116k km² on 1991-05-25 · max +12.1 °C · mean +7.9 °C · burden 631k km²·d · drift 275 km (39.9 N -8.7 E → 42.3 N -8.0 E)

116kkm²+12.1+0.0 °C1991-05-201991-05-28peak 1991-05-25centroid drift · 3.0° box

Event #2 — 1991-06-16 → 1991-06-22 7 dayshigh on 2/7 d only

peak 151k km² on 1991-06-19 · max +8.6 °C · mean +5.6 °C · burden 582k km²·d · drift 48 km (37.2 N 31.5 E → 37.5 N 31.9 E)

151kkm²+8.6+0.0 °C1991-06-161991-06-22peak 1991-06-19centroid drift · 1.8° box

Event #4 — 1991-06-17 → 1991-06-20 4 daysheat dome · 3/4 d · Z500 +171 m

peak 157k km² on 1991-06-18 · max +9.7 °C · mean +7.4 °C · burden 472k km²·d · drift 127 km (52.0 N 37.5 E → 52.8 N 38.8 E)

157kkm²+9.7+0.0 °C1991-06-171991-06-20peak 1991-06-18centroid drift · 1.3° box

Event #15 — 1991-09-27 → 1991-09-30 4 dayshigh on 2/4 d only

peak 136k km² on 1991-09-28 · max +11.0 °C · mean +7.4 °C · burden 451k km²·d · drift 20 km (43.5 N 26.0 E → 43.4 N 26.3 E)

136kkm²+11.0+0.0 °C1991-09-271991-09-30peak 1991-09-28centroid drift · 1.3° box

Event #3 — 1991-06-17 → 1991-06-20 4 dayshigh on 2/4 d only

peak 119k km² on 1991-06-18 · max +8.4 °C · mean +6.9 °C · burden 358k km²·d · drift 323 km (52.0 N 32.0 E → 54.2 N 35.0 E)

119kkm²+8.4+0.0 °C1991-06-171991-06-20peak 1991-06-18centroid drift · 2.8° box

Filled area is the event footprint in km² (left axis); the solid line is the peak anomaly inside it and the dashed line the mean (right axis). The small panel is the centroid path, circles sized by area and the ring marking day one. Drift is the straight-line start-to-end distance, so a dome that wandered and returned reports a small number.

Pipeline figures, 1991

Extent through the season

heatwave extent 1991

Footprints and tracks

heatwave events 1991