Myleene Klass is a ray of sunshine in a bright yellow plunging maxi-dress on hottest day of the year

Famke Janssen, 55, keeps cool in scorching NYC temperatures in off-the shoulder mini dress

Camila Mendes is cool in black sleeveless dress with buttons down the front in LA

Kate Mara dons a summery white dress on a stroll with her 13-month-old daughter in Los Angeles