Temperatures of up to 30 degrees are forecast this week as the second prolonged warm spell of the year takes hold. Met Éireann is anticipating highs in the mid- to high-20s throughout the week with little rain, peaking with a hot, humid day on Thursday that could reach 30 degrees in places.Sunday was forecast to reach 24 degrees in parts of the west coast, with sunshine widespread across the island.Cloud with a chance of rain or drizzle was expected on Monday morning, particularly in the northwest, before the mercury rises to between 21 and 27 degrees.Generally dry, warm weather is set to continue into Tuesday, becoming warmer again on Wednesday with highs in the mid-to-late 20s. “A hot and humid day with the chance of some heavier showers,” Met Éireann said of Thursday, with highs of between 24 and 30 degrees.The forecaster also warns of muggy evenings, with the temperature not dropping below the teens overnight on some nights.Conditions are set to turn cooler on Friday.The warm weather returns after May’s unusually early hot spell, which manifested in much of Europe as a severe heatwave. Ireland’s record for the hottest day was broken in “downright alarming” fashion by more than two degrees.The previous high temperature record for May was 28.4 degrees, logged at Ardfert, Co Kerry, on May 31st, 1997. That was before the “unusually early” spell of heat from May 23rd-27th last.On May 26th the weather station at Shannon Airport recorded 30.6 degrees. That record may also fall as seven other stations are believed to have broken it, with provisional temperatures as high as 30.9 degrees.Hot, dry air from North Africa has formed a dome over the Iberian Peninsula, trapping and pushing heat northwards to France and beyond.Heat domes are large, stationary areas of high pressure that block cooling for days or sometimes weeks. The record June temperature in Ireland is 33.3C, recorded at Kilkenny Castle in 1887. That is also the highest air temperature ever recorded in Ireland.Met Éireann encouraged people to be careful in the heat this week, and to exercise caution if entering water. The UV index will be high.Holidaymakers headed to Europe will face more extreme temperatures. France was facing a 40C day already on Sunday, and the country has placed emergency services and military forces on wildfire alert, restricting public alcohol consumption and cancelling some outdoor sporting events.In Italy, authorities have expanded heat warnings – referred to locally as “red flags” – for Sunday from seven to eight cities in northern and central parts of the country, out of the 27 monitored nationally by the health ministry.Temperatures in the “red” cities are mostly in the high 30Cs.Some cities in Spain had temperatures of 40C on Sunday, with the heatwave expected to persist through the week. – Additional reporting by agencies.