User:Timothy2b/sandbox v3

Gulf stream collapse
Järvsö has a cold version of the warm-summer humid continental climate (Dfb) according to the Köppen climate classification, and like most of Norrland features staggering seasonal differences. Summers are warm, very much so for its latitude, and see almost 20 hours of daylight on the summer solstice. Highs usually hover between 21 and 25 C, though frequently range between 25 and 30 C during heatwaves, with occasional peaks of above 30 C. Generally, highs above 20 C can be expected on most days from early June to late August. Nights remain cool, between 10 and 15 C on average, though may on the coolest ones fall to around 5 C. Tropical nights are rare, occurring on average only every other year. Summer and fall are usually the seasons that feature the most precipitation, and rainy periods, especially in the early and late part of summer, can see daytime highs below 20 C. "Högsommardagar" (high/peak summer days) occur 32 days annually, while highs reach the 30 C-mark on 3 days.

Winters are snowy, frigid, and very long, spanning almost half the year, and feature highs below freezing from early November to late March. Days see highs of -9 to -12 C from December to February, and nighttime lows hover between -17 to -20 C on most nights, and frequently fall below -20 C, doing so on average 21 nights annually. The coldest nights see temperatures below -30 C, occurring 4 times per season, with the coldest just above -40 C. Such conditions may feature highs below -25 C, but are usually brief, yielding to more bearable weather within a day or two. Typically, the mercury will not rise above freezing at all from late November to early-to-mid March, with warmer winter days seeing temperatures between -2 and -6 C. The Ljusnan begins to freeze at the end of October, becoming walkable by the start of November, and does not break up until mid-April. Snow cover lasts from late October or early November to the second half of April.

Spring and fall are short and volatile seasons, subject to swift swings in temperature in either direction, spring especially so. Spring begins in mid-April, with April featuring the infamous Swedish "aprilväder" (literally April weather) that can see summer-like temperatures followed by snowfall the next day. While rare, such swings can extend into early May. Nature begins to blossom out in mid-May, coinciding roughly with the arrival of meteorological summer. Fall arrives in mid-September, with fall foliage visible from early September to mid-October. The first snowfall typically occurs in mid-October, followed by a period of freeze-thaw cycles and slushy weather sometimes called "oktöber" (roughly Octhawber). Winter then arrives in late October.

The highest recorded temperature in Järvsö was registered at 36.2 C on August 4, 1975, while the hottest month on record was July 2018 with a mean of 23.2 C. That July also saw a record long streak of 10 days in a row above 30 C, and the hottest low of 22.1 C was on August 5, 1975, the day after the record high. The lowest temperature on record was -46.2 C on February 10, 1942, while the lowest high reached a meager -39.7 C on January 14, 2010. The coldest month ever was January 1987 with a mean of -27.2 C, while the longest continuous streak of sub-zero temperatures lasted 169 days from October 20, 1941, to April 6, 1942.

Annual precipitation amounts to an average of 430 mm, seeing higher amounts in summer and fall and lower ones in the spring. The spring thaw causes very high water discharge in the Ljusnan, though thanks to rising altitudes to the west, and thus delayed melting there, flooding is not particularly common as meltwater flows come progressively rather than all at once. Due to the abundance of meltwater reservoirs, summer droughts are rarely a problem. Järvsö receives an average of 170 cm of snowfall a year, the largest amounts falling from November to March, but multiple snow days also expected in October and April. Snowfall has occurred as early as September 21 and as late as May 17. Unlike the coastal parts of Hälsingland, Järvsö is not subject to much sea-effect snow coming off the Baltic, but rather sees small amounts accumulate over time. Still, the largest daily snowfall was 50 cm, which occurred on November 13, 2016, while the snowiest season was 1989-1990 with 244 cm. Snow depth tends to peak between 85 and 90 cm in mid-March, though did reach a depth of 180 cm in March 1966. The longest continuous snow cover lasted 209 days from October 12, 1941, to May 8, 1942.

The aurora borealis can fairly often be seen from Järvsö.

Seasonal averages:

Temperature change across the seasons.

Gulf stream collapse
Grand Rapids has a hot-summer humid continental climate (Dfa) according to the Köppen climate classification, and like most of the Midwest features vast seasonal differences. Summers are hot and humid, with highs usually hovering between 26 and 29 C, though humidity often making it feel quite a bit hotter. Heatwaves feature highs in the 30s °C (90s °C), driving heat indices upwards of 40 C, while cooler days see highs in the lower 20s °C (70s °F). Nights are pleasantly cool, typically dropping to 14 to 17 C, though can on the coolest nights drop to or below 10 C. During heatwaves, however, nights can get muggy, with tropical nights above 20 C. On average, 96 days a year feature highs above 25 C and 23 above 30 C.

Winters are cold and very snowy, courtesy of the city's location in the snow belt. Highs usually hover at -2 to -6 C, while nights fall to -8 to -13 C. Thaws can occur from time to time, but are very brief, seeing highs rise to 3 to 7 C, though nights remain below freezing. Cold snaps moving south from Canada can be brutal with highs staying below -10 C or even -20 C. Meanwhile, lows fall to -20 to -27 C, with temperatures below -30 C occurring about once every three years. On average, the mercury stays below the freezing mark for 82 days of the year. The Grand River freezes over in late November and breaks up in mid-March, while snow cover typically lasts from early December to mid-to-late March.

Spring and fall are rather short, bringing crisp and changeable weather. Spring begins in mid-March, seeing surges of warm, humid air from the Gulf of Mexico battling with the cold, dry Arctic air to the north. This is when the risk of tornadoes is at its greatest. While Michigan lies outside the general Tornado Alley, the aforementioned changes in air masses does nonetheless at times yield conditions suitable for tornado activity. Nature begins to leaf out in mid-April, with meteorological summer arriving in late April. True summer-like temperatures begin to settle in during mid-May. Summer then lasts through September, with meteorological fall arriving in mid-October. Fall foliage can be seen from late September to early November, typically peaking in mid-October. The increasing influence of Arctic air in the later stages of fall typically results in the first snow of the season falling in early November. Winter arrives during the second half of November, with freeze-thaw cycles repeating through the end of the month into early December when sub-zero temperatures take hold.

The highest recorded temperature at the airport was 42 C on July 13, 1936, which also happened to be the hottest month on record with a mean of 28.0 C. The Dust Bowl was known for its heatwaves, and a whopping 51 days in a row saw highs above 30 C that summer. The hottest daily low was 28 C on July 16, 1902. Conversely, the lowest temperature on record was -36 C on February 13-14, 1899, which also saw the coldest daily high of -26 C. The coldest month ever, on the other hand, was January 1977, with a mean of -18.6 C. The longest streak of sub-zero temperatures reached 109 days from November 23, 1989, to March 12, 1990.

Annual precipitation amounts to right around 1000 mm, with the largest amounts falling in the spring and early summer, with another peak in October. The spring thaw can occasionally lead to flooding along the Grand River, though downstream locations are more susceptible, especially on cold nights due to the potential for overnight ice accretion. Snowfall amounts to roughly 260 cm. Starting in November, lake-effect snow bands frequently blow in from Lake Michigan, growing especially powerful in December and January. As the lake freezes, these then become weaker, though snowfall remains high with particularly heavy events generated by Alberta clippers and Panhandle hooks. The largest of these events took place on December 16, 2016, when a powerful lake-effect cell dropped over 120 cm on the city over the course of 24 hours. This contributed to 2016-17 becoming the snowiest season on record, with 423 cm. Snowfall is heaviest from November to March, but can be expected a few days in April, with only occasional falls in October. Snow depth peaks during the second half of February, just prior to the spring thaw, usually reaching around 60 cm, though the record from February 2017 stands at 158 cm. The longest continuous snow cover lasted 150 days from November 17, 1989, to April 15, 1990.

Seasonal averages:

Temperature change across the seasons.