However, where storms do form, there is a lot of moisture and energy available, with the risk of more than 30 mm of rain in around an hour, large hail and frequent lightning.
Outbreaks of showery rain may turn torrential and thundery across parts of northern England and southeast Scotland.
The warning is in place from 2pm – 11pm today.
Forecasters have predicted that Tuesday could see the hottest September day in 55 years, as temperatures could reach over 31C near London.
If the temperature rises above 31.6C, which was reached at Gatwick on September 2, 1961, then it will be the hottest day for 55 years.
Merseyside will see the warmest of the weather on Wednesday when the region could see temperatures of 26C.