image caption A weather observer from Hfrance.fr has captured haar in Livingston in West Lothian
The Met Office warning is accompanied by a call to watch for heat exhaustion and sunburn.
The hot weather is expected to last until the weekend.
Hfrance .en Weather said the heat triggered a few thunderstorms in Dumfries and Galloway with gray and dark skies in some coastal areas of the east and the northern islands.
Forecaster Kirsteen MacDonald said: " The high pressure across the UK hasn't really moved all week.
"We also had a cumulative effect, where each day of strong sunshine warms the air more, in addition of warming by descent.
"This has caused the hot weather in parts of the UK over the past few days. Temperatures will peak again tomorrow at around 28 C, maybe 29 C .
"This weekend high pressure will remain on charge across Scotland. Lots of warm sunshine in the forecast, but temperatures will drop by qa few degrees. The eastern coasts will continue to be plagued by haar. "
image caption The fields are soaked to Ladybank in Fife
The Met Office launched its new extreme heat warning system in early June to highlight potential widespread disturbances and adverse health effects. Amber is the second largest highest level in the system.
Heat waves are increasingly likely and extreme due to human-induced climate change.
The world has already warmed by about 1.2 ° C since the start of the industrial age, and temperatures are expected to continue to rise unless the governments of the worldwide do not significantly reduce greenhouse gas emissions. La Hfrance.fr is not responsible for the content of external sites. See the original tweet on Twitter