Temperatures are set to soar as high as 28 degrees C in parts of Yorkshire on Tuesday following a more mixed weekend.
That will be followed by peaks of 29 degrees C on Wednesday as warm Caribbean air sweeps across the county.
In Leeds, weather will hit highs of 29 on Tuesday, but Sheffield's best weather will be on Wednesday with 30 degree heat.
Pollen and UV counts high
Residents have been warned that pollen counts will be high on Monday, Tuesday and Wednesday.
UV counts are also high all next week from Monday.
This weekend's weather
This weekend is expected to be largely dry and settled but less warm, with temperatures only hitting about 22 degrees.
Low pressure systems are set to move to the north west of the British Isles and with high pressure sitting to the east of the UK very humid air from the Caribbean is likely to be pulled our way.
In the meantime, there could be some thunder and lightning.
The Met Office forecast this week says:
Rain moving in during the morning, breaking up into heavy, locally thundery showers. Showers moving slowly eastward with wind easing, though perhaps persisting in the east. Maximum temperature 22 °C.
Outlook for Sunday to Tuesday:
Bright or sunny, largely dry on Sunday. Breezy overnight, with rain on hills. Wind easing on Monday. Becoming warm and largely sunny Monday and Tuesday, though cloudier over hills.