July 3: Long Lasting Heat Wave Starts Today

With high temperatures reaching the lower 90s in a few parts of the area, today officially marks the first day of what will be the longest heat wave in the last few years, and what will bring the hottest temperatures since June 2008 or August 2006. While humidity will not be very high at first, the humidity is expected to increase through next week, leading to a potentially dangerous heat index.

Tomorrow's Outlook:


While tomorrow had a few isolated 90s, tomorrow will bring more widespread 90s. High temperatures are expected to be in the lower to mid 90s inland and in the mid 90s for the immediate NYC area. Further east, high temperatures will be in the lower 90s for western Long Island, upper 80s to lower 90s for S CT and central/eastern Long Island, and in the lower 80s for the immediate coast.


As with the past few days, precipitation is not expected tomorrow, with sunny skies expected. Relatively low humidity is expected yesterday, which should not lead to a high heat index, however this will change later next week.


Early-Mid Next Week: Hottest Days Of The Summer


What could be the hottest days of the summer are likely to be early to mid next week. With the models having trended even warmer today, high temperatures in the lower 100s are likely for parts of the area on Tuesday and Wednesday.


Looking at the latest models, the NAM, which was actually too conservative for today, even shows high temperatures on Tuesday reaching the lower 100s for NE NJ, with the DGEX (which continues the NAM between hours 84-192) bringing NYC's temperature to 100 degrees on Wednesday and Thursday. The GFS is still hot, with high temperatures reaching the upper 90s to lower 100s for NYC and NE NJ, however its 18z run is considered an outlier, as its highs on Wednesday and Thursday are in the upper 90s to lower 100s, but it temporarily drops the temperatures to the upper 80s around 2 PM with no rain around. The 00z and 12z ECM runs continue with the extreme heat, bringing temperatures that would be even hotter than the NAM and GFS.


Overall, summarizing the trends of the last few days, the latest models, and the expected pattern, this is going to be a long lasting heat wave, where we may see over a week of 90+ degrees. Monday's high temperatures should be in the upper 90s with a few lower 100s for the immediate NYC area, with Tuesday, Wednesday and possibly Thursday being the hottest days, with high temperatures in the upper 90s to lower 100s, possibly in the higher end of that range. Humidity should start out relatively low, but will increase through next week, leading to the highest heat index taking place on Wednesday or Thursday.

Late Next Week And Next Weekend: Some Storms, Slightly Colder

The first sign of relief from the excessive heat should be with a weak cold front that should approach the area on Friday, and while Friday is likely to be dry at this time, a few isolated thunderstorms may be possible, with high temperatures only slightly cooling down, into the mid 90s. By Saturday, the cold front, despite being weak, may have a greater impact on the area, bringing the potential for scattered showers and thunderstorms, but with the warm air mass still around, high temperatures should still reach the lower 90s.

What happens afterwards becomes a question. A disturbance that is currently in the western Caribbean, which may become the second named storm of this year's Atlantic hurricane season, is shown to develop into a tropical depression or storm in the Gulf of Mexico next week on some models, while others do not develop it or bring it close to the US, which causes significant differences with the models for the pattern starting next weekend. Some models quickly bring in a colder air mass, while others keep the ridge around, with excessive heat lasting through the weekend.

At this time, I am leaning towards the slightly cooler solutions, but I still expect temperatures to remain above average through this time period. Stay tuned for more details on the longer range forecast, and what may happen with the tropical disturbance in the Caribbean.