Mýrdalsjökull is an exceedingly high precipitation location, with models suggesting parts of it receive more than 10 metres of rainfall equivalent annually.

[4]: 186–7  Jökulhlaup's 8000 to 6000 years ago took a path over the highest pass in the caldera wall which does not support a crater lake source but would happen with an ice cap.

[2]: 18  Any such studies related to climate change have to be qualified as past volcanic processes have resulted in the loss of up to 5% of the ice cap on more than one occasion.

[c] Most recent jökulhlaup (17 out of the 20 since the year 874) have descended to the east through Kotlujökull onto the Mýrdalssandur plain with about two large floods a century (i.e. presently overdue).

[d] However due to location factors of the original melt water, the Katla 934 and 1860 jökulhlaups also descended through Sólheimajökull to the Sólheimasandu flood plain.

It is perhaps not so significant from a hazard point of view as the 23 km2 (8.9 sq mi) water drainage catchment within the caldera rim northwest through Entujökull where a large jökulhlaup occurred in 874.

This En sector with total ice cap catchment of about 167 km2 (64 sq mi),[d] has rare but very large jökulhlaups every 500 to 800 years down the fairly well populated and developed Markarfljótsaurar flood plain.

There is a warning system which uses in the case of geothermal events the increased conductivity of the river waters and can detect seismic flood tremor.

[1]: 28, 31  This has been assigned a 89% probability within 30 years, affecting possibly the town of Vík, likely associated with eruption of 1.5 km3 (0.36 cu mi) of tephra (so disruptive to air travel)[f] and likely occurring in the months June to September.

[1]: 74  There is a lower probability of an Entujökull jökulhlaup of the same size which is expected to have far graver environmental, social and geomorphological consequences affecting the town of Hvolsvöllur and surrounds.