Sri Vijaya Puram, July 17: Thunderstorm with gusty wind (30-40 kmph) and lightning is very likely to occur at one or two places over A&N Islands on July 18. Squally weather with surface wind speed reaching 35-45 kmph gusting to 55 kmph is very likely over South Andaman Sea. Sea conditions are likely to be rough. Fishermen have been advised not to venture into the sea along and off South Andaman Sea from July 18 to 21.