Several non-urgent operations have been postponed at the Princess Elizabeth Hospital and the issue is expected to last for several days.
Health and Social Care say the incident is not weather related, as the island enters an official heatwave, and A&E is seeing an increase in demand and waiting times.
Yesterday, temperatures hit 32C, the hottest day in May on record.
One elective operation (deemed non-urgent) is being postponed today, while two were cancelled yesterday (26 May).
Hospital bosses say emergency and cancer surgery will continue.
Extra 'flex' beds are being added to the wards and community staff are taking on a greater caseload as patients are discharged to ease pressure on the hospital.
Heath and Social Care apologises to those affected, but says patient safety is a priority.
It expects the capacity issue to last for several days.
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