Britain is set to outshine Honolulu on Friday, with parts of the country climbing towards 27C ahead of the May Day festivities and the long bank holiday weekend. But forecasters warn the early‑summer feeling may be short-lived, with heavy rain and thunder waiting in the wings. The London–East Anglia corridor is expected to see the year’s warmest temperatures so far, possibly nudging some areas past the 26C forecast for Hawaii’s capital. Elsewhere, Edinburgh may be warmer than Athens, with temperatures of 18C, compared to the Greek capital's forecast highs of just 14C for Friday. Temperatures are around 10C above average for early May, though still shy of the April record of 29.4C set in 1949.…