When to expect the first freeze

The weather has been somewhat boring here in New England over the past few days, with not much to talk about. I wanted to share a quick post about one of the fall firsts that excites me every year - the first freeze.

(NOAA)

This information is especially important for gardeners, who need to care for their plants. Here in New England, the median date of the first 32 °F temperature reading ranges from Nov 1-10 in far southwest Connecticut to Aug 21-31 near Mount Washington in New Hampshire. In Addison County in Vermont, the first freeze tends to occur in mid to late September.

The above climatological map was created by determining the median first date when the temperature falls below 32 °F. However, frost can occur when the temperature is 36 °F, but a hard freeze generally happens at 28 °F. I am not sure if the above map uses temperature readings at 2 meters above the surface (where the temperature is officially recorded) or at the surface. In that small difference between the ground and 2 meters above the ground, there can definitely be a temperature difference, especially at night. When gardening during the fall, it is important to err on the side of caution if the temperature looks to be nearing 35 °F overnight.

September

Happy Labor Day! 

It's a windy day here in the North Country, especially on Lake Champlain, where gusts will approach 50 mph at points during the day.

Before I take a brief look at some climatology in Vermont for September, I wanted to share a photo of a beautiful sunset that I took the other night - for me, views like this are quintessential Vermont.

September is one of my favorite months of the year. It is a very transitional month, marking the start of the school year for many, the start of fall, and the shift away from muggy and hot weather towards refreshing and cool air. With September having just started, I wanted to take a look at climate data from past Septembers for Burlington International Airport (BTV) in Burlington, VT.

At BTV, the mean high temperature in September is 70.4 °F. The graph below shows mean September high temperatures at BTV for all years since 1941.

(NOAA Regional Climate Centers/xmACIS)

As the red regression line shows, the mean of September daily high temperatures has been trending upwards, and they range from 64.9 °F in 1950 to 78.9 °F in 2015.

The mean low temperature in September at BTV is 50.1 °F. The following graph shows mean September low temperatures at BTV for all years dating back to 1941.

(NOAA Regional Climate Centers/xmACIS)

Similar to mean high temperatures for September, the mean of September daily low temperatures at BTV has been trending up. The lowest mean low temperature for September was 40.2 °F in 1963, and the highest was 56.4 °F in 2018.

One of my favorite parts of September in Vermont is the foliage that illuminates our state. Here is a photo that I took in Wilmington in southern Vermont a few years ago.

The colors can simply be incredible. By late September in northern Vermont, we can expect to near peak foliage. Hopefully, despite the dry summer that we had, the fall colors will show themselves fully this year.

Whirlwind weather out west

I don't normally talk about locations other than New England on this blog, but I simply had to discuss what is set to happen in the west on this post.

In Colorado, in a matter of days, the temperature will dip from near 100 °F to around 30 °F.

GFS temps through Thursday (Tropical Tidbits)

Take a look at how rapidly those temperatures in Colorado dip over ~ a 36 hour period. Specifically, in Denver, the National Weather Service forecast calls for temperatures to drop from 87 °F on Monday at 3 p.m. to 30 °F on Wednesday at 6 a.m. Thats crazy! Talk about a whirlwind period of weather for those that live in Colorado.

NWS Boulder forecast for Denver

Additionally, snow could accumulate in Denver by Wednesday morning. We could see areas in Colorado be above 90 °F and then have accumulating snowfall in a matter of days!

What is causing this dramatic change in the weather out west? A cold frontal passage will move south through Colorado, as you can see in the forecast map below.

NWS 48 hour forecast map (NWS)

It'll be very exciting to see how dramatic this drop in temperatures is!

VT Summer 2020 Recap

This post is my last one in the four-part series that recapped August and summer 2020 weather in Connecticut and Vermont. For yesterday's recap of summer 2020 weather in Connecticut, see the link here. Meteorological summer is defined as June 1 to August 31, so that period will be the focus of this post. Again, I will focus on Burlington International Airport (BTV) in Burlington, VT.

Temperatures

We had one daily high record temperature set this summer, occurring on June 23. On that date, BTV had a high temperature of 96 °F, which broke the previous June 23 record of 93 °F. For me, the most interesting record of the summer of BTV was the greatest number of consecutive days where the temperature did not drop below 60 °F. On August 6, the temperature dropped below 60 °F for the first time in 41 days, breaking the old streak record of 37 days, set in 1898.

(NOAA Regional Climate Centers/xmACIS)

There were 3 heatwaves at BTV this summer, the longest of which being 6 days and ending on June 23. In summer 2019, there were no heatwaves at BTV. The daily high temperature recorded in Burlington was greater than or equal to 90 °F on 18 different days this summer. In a normal summer, we'd only have 4.8 days where the maximum temperature is >= 90 °F.

To further examine the temperatures of the summer, I like to look at cooling degree days (CDD), which are a measurement that attempts to determine how much energy is needed to cool buildings (with 65 °F being the temperature to which they get cooled). This summer, we had 766 CDDs, which is a record for BTV. If you had air conditioning, you likely spent a lot of money on it this summer.

Total historical summer cooling degree days for BTV (NOAA Regional Climate Centers/xmACIS)

Like at Bradley International Airport in Connecticut, BTV had its warmest summer on record this year, with an average temperature of 72.3 °F, breaking the old record of 72.2 °F set in 1949. In a normal year, the average temperature would be 68.4 °F, giving us a departure from normal of 3.9 °F.

Historical summer average temperatures (°F) at BTV (NOAA Regional Climate Centers/xmACIS)

Summertime temperatures have been trending upwards, as evidence by the positive sloping regression line in the above graph. It is significant, though, that summer 2020 was the warmest on record.

Precipitation

In terms of precipitation, BTV had a fairly typical summer, though slightly dry. We had 10.94 inches of rainfall this summer, when a normal year as 11.76 in., meaning that 93% of the expected total precipitation fell this summer. Though we were mostly dry this summer and playing catchup to "normal precipitation" (the brown line in the graph below) on August 11 and 12 we had actually accumulated more summertime rain than the expected amount for those days.

BTV summer 2020 accumulation (NOAA Regional Climate Centers/xmACIS)

The big upward trend in the above graph occurred thanks to Tropical storm Isaias, which brought 2.50 in. of rain to BTV on August 5. Also, note that it was especially dry during June, when the green line really does not slope upwards at all.

While BTV did see a fairly normal total summer precipitation this year, much of the state was very dry, as evidenced in the map below.

 (NOAA Regional Climate Centers)

While Burlington, VT is abnormally dry right now, eastern parts of the state are experiencing a moderate drought.

Wrap Up

Summer is always a spectacular time to be in Vermont, and this summer did not disappoint. Though it was hot, there were some spectacular weather days. Isaias brought some much needed rain to the state on August 4, and there were some exciting convective storms throughout the summer.

Vermont is known for its fall foliage. This year, however, I'm curious as to how radiant it will be, since it was so dry this summer. We'll have to wait and see!

CT Summer 2020 Recap

Meteorological summer has ended, and it is now time to take a look at the big climate stories in Connecticut for summer 2020. As I've discussed on this blog all summer, it has been hot and dry. The data don't lie, so let's take a look at things. Again, I'll be using Bradley International Airport (BDL) as my location for the data. Note that the weather at BDL is not indicative of what happened throughout the state this summer (it's especially different from the shoreline). I'll also mention that meteorological summer lasts from June 1 to August 31, so anything that I discuss in this blog post is related to that time frame.

Temperatures

It was a summer for records, and we started summer on day 1 with a cold temperature record. On June 1, the temperature at BDL dipped to 37 °F, one degree lower than the previous low temperature record which was set in 2001. The June 3 low temperature record of 42 °F was also tied this summer. After these two low temperature records kicked of summer on a cool note, the heat cranked up.

BDL summer 2020 temperature data (NOAA Regional Climate Centers/xmACIS)

On July 27th and 28th, and again on August 23rd and 24th, daily high temperature records were set at BDL. July 19th was the day with the hottest temperature this summer at 99 °F, but it did not even tie that day's record, which is 100 °F set in 1991. We had 6 heatwaves this summer, and the longest one was 8 days, ending on August 1st. That 8 day heatwave ties for the fifth longest heatwave on record.

Officially, the mean temperature at BDL for summer 2020 was 74.4 °F, which ties the record for the warmest summer at BDL, set in 1973. The average mean summer temperature at BDL is 71.4 °F.

BDL historical summer mean temperatures (NOAA Regional Climate Centers/xmACIS)

Although we did have a record warm summer this year, that is no crazy anomaly. Summertime temperatures have been getting higher in CT, as evidenced by the red regression line in the graph above. 

(NOAA Regional Climate Centers)

It was a record setting summer at BDL, but it was also extremely hot throughout the state. In the above map, you can see that temperatures ran between 2 and 4 °F above normal this summer in almost all of Connecticut. Bridgeport had a 3.2 °F departure from normal while BDL's was 3.0 °F.

Precipitation

BDL was especially dry this summer - in fact, it was the driest summer on record. We saw 4.42 inches of total precipitation, when a "normal" summer would have 12.40 inches. This means we saw only 36% of the average rainfall for BDL this summer.

BDL Summer 2020 accumulation (NOAA Regional Climate Centers/ xmACIS)

Right from the start of the summer, we were slow to pick up any significant precipitation, as evidenced from the accumulation graph above.

The following graph shows just how dry it was this summer when compared to other summers. Notice how 2020 had the least total precipitation.

BDL historical summer total rainfall (NOAA Regional Climate Centers/xmACIS)

Interestingly, there was a large disparity in the rainfall we saw throughout the state. While BDL had 36% of its normal rainfall, Bridgeport had 99% of its normal precipitation. In Connecticut, the further north and west you were this summer, the more likely you were to have an abnormally dry summer.

(NOAA Regional Climate Centers)

Wrap up

A drought persists for much of Connecticut, especially in northern parts of the state. The main causes of this drought are the lack of rain and the warm temperatures that we had this summer. 

Connecticut had its fair share of severe weather this summer - from severe convective storms that brought large hail to a few tornadoes in August to Tropical Storm Isaias. For me though, the big story was the heat and the dryness. Hopefully fall will bring some more precipitation, since we definitely need it.

VT August Recap

For my second post in a series that'll recap August and summer 2020 weather, I'll take a look at this past August in Vermont. Yesterday, I examined weather for Connecticut during August 2020.

Isaias

Tropical Storm Isaias passed through Vermont on August 5th, dumping rain on the state but causing less extensive damage than the storm did in Connecticut.

Precipitation from Isaias (NWS Burlington)

The above map shows that the heaviest rainfall totals were felt directly along the path of Isaias, while parts of eastern Vermont like the Northeast Kingdom, which were slightly east of Isaias' path, averted the worst of the rain. Aside from a 70 mph wind gust that blew on Mount Mansfield, Isaias' strongest winds in Vermont were around 50 mph in the Champlain Valley.

Temperatures

Temperatures averaged 2.2 °F above normal in August 2020 at Burlington International Airport (BTV), where a first-order weather station is located. The average temperature for the month was 71.0 °F, and normal for August is 68.8 °F. While BTV has seen an unusually large number of days where the high temperature reached 90 °F this summer, the temperature topped 90 °F on only two days in August, the 10th and the 11th. On the 11th, the temperature hit 92 °F.

(NOAA Regional Climate Centers/xmACIS)

We had our coolest day of the month on the 27th, when the temperature dipped to 48 °F. There was only one day in August when the overnight low temperature failed to drop below 70 °F - August 11th.

Precipitation

New England has been very dry this summer, but Vermont saw some much needed precipitation this past month. BTV received 6.61 inches of rain, and average for August is 3.91 in. A large part of the month's rain came from Isaias, when 2.50 in. of rain fell at BTV.

(NOAA Regional Climate Centers/xmACIS)

The above accumulation graph shows that we saw significant precipitation on a few days due to convective storms and Isaias, and that we were well above normal (the brown line) for the entire month. Interestingly, August 2020 was the 5th warmest August on record at BTV, and records for the airport date back to 1940.

Wrap up

Overall, it was a warm, but wet month here in Vermont. While severe drought conditions persist in parts of Connecticut, much of Vermont is only abnormally dry or in a moderate drought. September in Vermont is spectacular, as temperatures tend to be comfortable and the leaves start to show their fall colors. It'll be exciting to see what this September's weather has in store.

CT August Recap

This post will be the first in a series of posts where I recap the weather of August and summer 2020 for Connecticut and Vermont. There's a lot to cover in these posts, so we'll get right to it.

Isaias

The big story for Connecticut was Tropical Storm Isaias, which wreaked havoc in the state on August 4th. Unlike past extreme weather events that I've lived through in Connecticut, practically no region of the state was spared during Isaias, as power outages and damage occurred throughout the entire state.

(PowerOutage.US)

The above map shows power outages in the state on during the evening after Isaias moved through southern New England, and I think the most telling aspect of it is the consistency of the reds and oranges in Connecticut. This underscores the fact that Isaias' impacts were widespread throughout the state. Aside from straight-line winds that reached 85 mph, Isaias produced a tornado in Westport and a deluge of rain. The storm will go down as one of the more memorable events in Connecticut weather history.

Tornadoes

While not known as a tornado hot spot, Connecticut saw its fair share of tornadoes this August. 5, to be exact. On Sunday, August 2, just before Isaias was set to strike the state, an EF-0 tornado hit Sharon and an EF-1 tornado passed through Falls Village. As I mentioned above, there was a tornado associated with Isaias in Westport on August 4. Just a few days ago, on the 27th, the National Weather Service confirmed that an EF-1 tornado touched down in Bethany, and a EF-0 tornado struck Kent. August 27th was an active weather day throughout the state, as storms moved southeast and caused unusually large hail for Connecticut and power outages in some areas.

August 28th in Branford (Peter Hvizdak/Hearst Connecticut Media)

Temperatures

As has been the case all summer, August was a hot month in Connecticut. At Bradley International Airport (BDL) in Windsor Locks, CT, where a first-order weather station is located, the August 2020 average temperature was 74.6 °F, when normal is 71.9 °F, giving us an temperature departure from normal of 2.7 °F for the month. This average makes August 2020 the 6th warmest on record at BDL, and records date back to 1949 at the airport. There were two heat waves this month; the first lasted 5 days and ended on the 12th and the second was a 3 day heat wave that ended on the 23rd. The month's highest temperature was 96 °F, which occured on the 10th.

(NOAA Regional Climate Centers/xmACIS)

Daily record high temperatures were achieved on August 23rd and 24th. On both days, the high temperature reached 93 °F, which is a fairly weak record. (You can see this by looking at the above graph, which shows that the red shaded range which shows high temperature records dip slightly on the 23rd and 24th).

Yesterday (the 31st), was a very comfortable day, and we actually had the coolest temperature of the month at 48 °F, which you can see from the lower bar on the above graph for the 31st. Mostly, though, low temperatures were in the 60s, and we had 5 days where the overnight low temperature only did not dip below 70.

Precipitation

BDL saw 2.20 inches of rain this month, which, despite being only 0.02 in. less than what we saw in June and July combined, was still less than the August average of 3.93 inches. On the day that Isaias passed through Connecticut, only 0.15 inches of rain fell, showing that the storm produced minimal precipitation in the northern part of the state near BDL.

Aug 2020 accumulated precipitation (NOAA Regional Climate Centers/xmACIS)

We received the month's greatest rainfall total on the 27th, when 0.60 inches of rain fell on the big severe weather day in the state. While we did have more precipitation this August than we did in June and July, it was still quite dry and little was done to alleviate the drought that persists in Northern Connecticut.

Wrap up

August 2020 was a exciting and hectic weather month in Connecticut. We saw five tornadoes and a major tropical storm passed through the state, causing significant damage. As has been the trend all summer, it was warm and dry this month, and the drought persists in the state. We are now entering September, which marks the start of meteorological fall and one of my favorite times of the year. It'll be interesting to see what occurs weather-wise this month!