Mew Lake Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mew Lake Campground clear sky chart from 2005-11-06 to 2024-04-03.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	17% 12% 5% 9% 7% 3 4 4 4 6% 28%	79172
	Night	15% 14% 6% 10% 7% 4 5% 4 4 6% 27%	80940
Transparency	Day	57% 5% 9% 18% 9% 1	78875
	Night	59% 5% 10% 16% 9% 1	80773
Seeing	Day	24% 18% 31% 18% 7% 2	13927
	Night	23% 16% 31% 21% 8% 1	22912

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	13% 19% 8% 17% 9% 3 4 3 4 4 15%	2517
	11th to 20th	Day	11% 13% 8% 18% 15% 4 4 4 5% 4 13%	2520
	21st to end	Day	16% 21% 12% 13% 6% 3 4 3 2 4 17%	3124
February	1st to 10th	Day	10% 17% 8% 13% 12% 4 6% 4 4 5% 17%	1710
	11th to 20th	Day	10% 15% 8% 12% 10% 4 6% 4 5% 6% 22%	1663
	21st to end	Day	15% 16% 6% 10% 9% 4 5% 5% 4 5% 20%	1451
March	1st to 10th	Day	14% 14% 5% 12% 7% 4 5% 4 4 5% 26%	2044
	11th to 20th	Day	12% 15% 7% 10% 8% 5% 4 4 4 4 26%	2090
	21st to end	Day	16% 13% 5% 8% 5% 3 4 3 4 5% 35%	2313
April	1st to 10th	Day	20% 16% 6% 8% 5% 3 3 4 4 6% 26%	2184
	11th to 20th	Day	20% 11% 5% 7% 5% 3 4 3 4 5% 34%	2188
	21st to end	Day	20% 14% 4 7% 5% 2 3 3 3 6% 32%	2340
May	1st to 10th	Day	19% 11% 3 7% 5% 3 4 4 4 7% 33%	2443
	11th to 20th	Day	19% 9% 4 6% 6% 3 4 4 3 6% 35%	2478
	21st to end	Day	15% 7% 4 6% 6% 3 5% 4 5% 7% 39%	2725
June	1st to 10th	Day	21% 9% 4 6% 5% 3 5% 4 6% 7% 30%	2520
	11th to 20th	Day	16% 7% 3 5% 5% 3 5% 6% 5% 8% 37%	2631
	21st to end	Day	18% 8% 3 6% 6% 4 6% 5% 5% 8% 32%	2700
July	1st to 10th	Day	14% 5% 2 5% 6% 4 6% 5% 7% 8% 38%	2679
	11th to 20th	Day	13% 6% 4 6% 6% 5% 5% 5% 6% 8% 36%	2520
	21st to end	Day	14% 7% 3 7% 7% 3 6% 6% 5% 9% 33%	2728
August	1st to 10th	Day	15% 7% 3 6% 7% 4 6% 6% 5% 8% 33%	2327
	11th to 20th	Day	16% 7% 3 5% 7% 4 5% 6% 7% 7% 34%	2303
	21st to end	Day	15% 7% 3 7% 6% 5% 5% 5% 6% 8% 32%	2466
September	1st to 10th	Day	16% 8% 3 5% 5% 3 5% 5% 6% 7% 38%	2160
	11th to 20th	Day	17% 6% 4 5% 5% 3 4 4 5% 6% 41%	2122
	21st to end	Day	20% 9% 3 7% 6% 3 5% 5% 4 6% 33%	1904
October	1st to 10th	Day	21% 10% 4 6% 5% 3 5% 4 4 6% 32%	1800
	11th to 20th	Day	25% 16% 5% 7% 7% 4 4 3 4 5% 20%	1800
	21st to end	Day	29% 16% 6% 8% 6% 3 3 3 4 4 18%	1956
November	1st to 10th	Day	16% 16% 5% 8% 6% 3 4 4 4 7% 26%	1528
	11th to 20th	Day	17% 18% 7% 13% 6% 3 4 3 4 5% 20%	1520
	21st to end	Day	20% 20% 9% 12% 6% 4 4 4 4 3 13%	1520
December	1st to 10th	Day	18% 23% 9% 12% 7% 3 4 3 4 5% 13%	1520
	11th to 20th	Day	15% 21% 11% 11% 8% 4 4 3 3 4 16%	1906
	21st to end	Day	21% 22% 9% 13% 9% 2 2 2 2 3 14%	2772
January	1st to 10th	Night	14% 20% 10% 15% 9% 4 5% 5% 4 4 11%	4429
	11th to 20th	Night	10% 15% 7% 16% 17% 7% 6% 4 4 4 11%	4436
	21st to end	Night	14% 18% 11% 15% 7% 4 6% 4 3 3 15%	4532
February	1st to 10th	Night	11% 16% 8% 12% 10% 6% 5% 5% 5% 6% 17%	2470
	11th to 20th	Night	10% 14% 8% 12% 8% 4 5% 4 5% 5% 24%	2403
	21st to end	Night	11% 16% 7% 12% 8% 5% 6% 4 5% 5% 21%	2003
March	1st to 10th	Night	12% 13% 6% 11% 7% 3 5% 4 4 5% 30%	2119
	11th to 20th	Night	12% 14% 6% 9% 7% 4 5% 4 4 6% 30%	2089
	21st to end	Night	12% 12% 5% 8% 6% 3 4 4 5% 6% 36%	2284
April	1st to 10th	Night	19% 15% 6% 7% 4 3 4 3 4 7% 29%	1821
	11th to 20th	Night	17% 11% 5% 6% 4 3 3 4 4 5% 37%	1737
	21st to end	Night	20% 10% 4 8% 6% 3 5% 4 4 5% 31%	1620
May	1st to 10th	Night	18% 8% 3 7% 5% 2 4 5% 6% 8% 36%	1517
	11th to 20th	Night	17% 8% 2 4 4 3 4 4 5% 8% 40%	1415
	21st to end	Night	12% 7% 3 6% 4 3 4 5% 5% 8% 44%	1550
June	1st to 10th	Night	17% 8% 4 6% 5% 3 5% 5% 5% 6% 35%	1440
	11th to 20th	Night	15% 6% 2 5% 5% 2 5% 5% 4 8% 44%	1324
	21st to end	Night	15% 9% 4 6% 5% 2 5% 5% 6% 8% 36%	1260
July	1st to 10th	Night	10% 6% 2 5% 5% 3 3 4 5% 8% 47%	1276
	11th to 20th	Night	12% 7% 3 6% 4 3 4 4 4 8% 45%	1440
	21st to end	Night	11% 6% 2 4 5% 3 6% 5% 6% 8% 44%	1587
August	1st to 10th	Night	12% 5% 3 5% 4 2 4 5% 6% 8% 45%	1611
	11th to 20th	Night	10% 6% 2 5% 5% 4 6% 6% 6% 7% 44%	1598
	21st to end	Night	13% 6% 3 5% 5% 3 5% 4 7% 9% 40%	1871
September	1st to 10th	Night	12% 6% 2 5% 3 3 4 5% 5% 7% 46%	1800
	11th to 20th	Night	15% 9% 3 5% 4 2 3 3 5% 7% 45%	1836
	21st to end	Night	18% 8% 3 7% 4 3 4 4 4 7% 39%	2056
October	1st to 10th	Night	20% 10% 3 5% 4 3 4 5% 4 6% 35%	2160
	11th to 20th	Night	23% 14% 3 7% 5% 3 4 4 5% 5% 25%	2160
	21st to end	Night	25% 17% 5% 8% 5% 3 4 3 4 5% 21%	2398
November	1st to 10th	Night	17% 15% 5% 7% 5% 3 5% 4 4 5% 29%	2546
	11th to 20th	Night	17% 15% 6% 9% 7% 3 5% 4 5% 6% 23%	2660
	21st to end	Night	17% 21% 7% 10% 8% 4 5% 4 3 5% 16%	2660
December	1st to 10th	Night	17% 23% 10% 14% 8% 3 3 3 4 3 12%	2660
	11th to 20th	Night	14% 21% 10% 12% 8% 3 4 3 3 4 17%	3288
	21st to end	Night	21% 22% 8% 14% 9% 3 4 3 3 3 11%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	73% 3 9% 8% 6%	2518
	11th to 20th	Day	73% 6% 6% 10% 5% 1	2520
	21st to end	Day	74% 3 5% 10% 6% 1	3124
February	1st to 10th	Day	70% 4 6% 13% 6% 1	1710
	11th to 20th	Day	64% 4 10% 12% 9% 1	1672
	21st to end	Day	66% 5% 7% 12% 9% 1	1451
March	1st to 10th	Day	61% 4 11% 12% 10% 2	2047
	11th to 20th	Day	62% 4 8% 15% 9% 2	2090
	21st to end	Day	52% 4 8% 17% 14% 4	2313
April	1st to 10th	Day	60% 4 9% 17% 9% 2	2184
	11th to 20th	Day	54% 4 7% 22% 11% 2	2188
	21st to end	Day	56% 4 7% 17% 12% 3	2340
May	1st to 10th	Day	51% 4 9% 19% 12% 3	2443
	11th to 20th	Day	51% 5% 7% 22% 13% 2	2482
	21st to end	Day	45% 7% 11% 20% 13% 3	2725
June	1st to 10th	Day	53% 6% 10% 20% 11% 1	2520
	11th to 20th	Day	45% 6% 10% 23% 14% 2	2631
	21st to end	Day	51% 6% 12% 20% 10% 1	2700
July	1st to 10th	Day	41% 6% 12% 27% 12% 1	2606
	11th to 20th	Day	44% 7% 12% 26% 10% 1	2445
	21st to end	Day	46% 7% 12% 25% 9%	2575
August	1st to 10th	Day	47% 8% 14% 21% 9% 1	2314
	11th to 20th	Day	46% 8% 15% 23% 8% 1	2303
	21st to end	Day	48% 7% 13% 21% 10% 1	2466
September	1st to 10th	Day	44% 6% 12% 25% 12% 1	2160
	11th to 20th	Day	44% 6% 12% 27% 11%	2122
	21st to end	Day	53% 6% 10% 24% 7%	1904
October	1st to 10th	Day	54% 6% 11% 18% 10% 1	1800
	11th to 20th	Day	68% 5% 10% 12% 5% 1	1800
	21st to end	Day	70% 4 8% 11% 6% 1	1956
November	1st to 10th	Day	58% 5% 13% 17% 5% 1	1528
	11th to 20th	Day	67% 5% 9% 12% 6% 1	1520
	21st to end	Day	76% 5% 8% 8% 4 1	1520
December	1st to 10th	Day	75% 4 6% 9% 4 1	1520
	11th to 20th	Day	74% 3 6% 8% 7% 1	1906
	21st to end	Day	77% 3 4 12% 4	2772
January	1st to 10th	Night	76% 5% 9% 7% 3	4429
	11th to 20th	Night	75% 6% 7% 7% 4 1	4436
	21st to end	Night	75% 3 6% 8% 6% 1	4532
February	1st to 10th	Night	67% 6% 9% 11% 6% 1	2470
	11th to 20th	Night	63% 4 9% 16% 8% 1	2405
	21st to end	Night	64% 4 7% 16% 8% 1	2003
March	1st to 10th	Night	57% 4 10% 15% 11% 2	2129
	11th to 20th	Night	56% 5% 11% 16% 10% 1	2090
	21st to end	Night	49% 5% 8% 20% 14% 3	2284
April	1st to 10th	Night	57% 4 7% 19% 12% 2	1821
	11th to 20th	Night	51% 4 6% 23% 15% 1	1737
	21st to end	Night	55% 5% 7% 16% 15% 2	1620
May	1st to 10th	Night	45% 6% 11% 20% 15% 3	1517
	11th to 20th	Night	43% 6% 8% 24% 17% 2	1416
	21st to end	Night	39% 7% 15% 20% 16% 3	1551
June	1st to 10th	Night	48% 5% 11% 21% 12% 1	1440
	11th to 20th	Night	39% 6% 13% 26% 16% 1	1324
	21st to end	Night	46% 6% 15% 21% 11% 1	1260
July	1st to 10th	Night	32% 7% 14% 26% 19% 1	1241
	11th to 20th	Night	39% 6% 13% 29% 12% 1	1392
	21st to end	Night	35% 8% 17% 28% 11% 1	1499
August	1st to 10th	Night	36% 8% 17% 26% 12% 1	1600
	11th to 20th	Night	36% 9% 19% 26% 9% 1	1598
	21st to end	Night	40% 7% 17% 26% 10% 1	1871
September	1st to 10th	Night	36% 8% 16% 27% 12% 1	1800
	11th to 20th	Night	40% 5% 13% 30% 11%	1836
	21st to end	Night	46% 6% 12% 28% 8%	2056
October	1st to 10th	Night	50% 6% 11% 19% 14%	2160
	11th to 20th	Night	60% 7% 12% 16% 6%	2160
	21st to end	Night	67% 4 8% 12% 8% 1	2398
November	1st to 10th	Night	58% 5% 12% 18% 7%	2546
	11th to 20th	Night	63% 6% 12% 12% 6% 1	2660
	21st to end	Night	72% 5% 10% 9% 4	2660
December	1st to 10th	Night	78% 5% 6% 8% 3	2660
	11th to 20th	Night	72% 4 6% 12% 7%	3288
	21st to end	Night	80% 3 5% 7% 4	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	26% 24% 32% 12% 4 1	180
	11th to 20th	Day	29% 19% 34% 13% 3 1	180
	21st to end	Day	26% 19% 36% 14% 5%	297
February	1st to 10th	Day	28% 29% 33% 6% 3	270
	11th to 20th	Day	26% 33% 34% 7%	270
	21st to end	Day	37% 23% 31% 8% 1	263
March	1st to 10th	Day	25% 23% 37% 13% 2	460
	11th to 20th	Day	24% 24% 34% 13% 4 1	460
	21st to end	Day	27% 24% 30% 14% 4	506
April	1st to 10th	Day	25% 24% 34% 12% 4 1	428
	11th to 20th	Day	31% 21% 23% 14% 8% 3	412
	21st to end	Day	29% 18% 32% 13% 6% 1	420
May	1st to 10th	Day	27% 16% 29% 20% 6% 2	423
	11th to 20th	Day	24% 19% 30% 17% 8% 2	447
	21st to end	Day	20% 19% 29% 21% 8% 3	485
June	1st to 10th	Day	25% 13% 36% 21% 5% 1	450
	11th to 20th	Day	18% 14% 35% 21% 10% 2	561
	21st to end	Day	21% 14% 34% 22% 8% 1	630
July	1st to 10th	Day	13% 12% 34% 30% 9% 1	601
	11th to 20th	Day	17% 13% 32% 24% 11% 3	444
	21st to end	Day	13% 13% 34% 29% 8% 2	488
August	1st to 10th	Day	17% 9% 33% 27% 9% 6%	446
	11th to 20th	Day	16% 8% 28% 30% 12% 6%	439
	21st to end	Day	18% 13% 32% 21% 11% 5%	495
September	1st to 10th	Day	18% 12% 34% 19% 12% 5%	450
	11th to 20th	Day	21% 10% 27% 23% 14% 6%	450
	21st to end	Day	22% 17% 26% 20% 11% 3	450
October	1st to 10th	Day	26% 19% 24% 16% 11% 2	450
	11th to 20th	Day	32% 22% 30% 12% 3 1	450
	21st to end	Day	39% 18% 27% 14% 2	482
November	1st to 10th	Day	30% 23% 32% 12% 3	222
	11th to 20th	Day	34% 19% 31% 11% 4	180
	21st to end	Day	34% 20% 35% 9% 1 1	180
December	1st to 10th	Day	31% 21% 33% 14% 1	180
	11th to 20th	Day	34% 27% 29% 8% 1 1	180
	21st to end	Day	29% 29% 25% 14% 3 1	198
January	1st to 10th	Night	25% 21% 36% 14% 3	760
	11th to 20th	Night	27% 21% 31% 17% 4 1	760
	21st to end	Night	18% 19% 35% 21% 6% 1	836
February	1st to 10th	Night	20% 24% 38% 15% 3	760
	11th to 20th	Night	20% 21% 39% 16% 3	743
	21st to end	Night	23% 23% 32% 19% 3	628
March	1st to 10th	Night	21% 25% 32% 19% 3	760
	11th to 20th	Night	22% 19% 37% 16% 5% 1	760
	21st to end	Night	19% 20% 33% 21% 6%	836
April	1st to 10th	Night	28% 16% 33% 19% 4	729
	11th to 20th	Night	26% 17% 28% 20% 9% 1	673
	21st to end	Night	25% 12% 29% 23% 11%	540
May	1st to 10th	Night	24% 9% 27% 29% 10% 1	437
	11th to 20th	Night	22% 11% 34% 26% 8%	354
	21st to end	Night	16% 10% 37% 27% 11%	389
June	1st to 10th	Night	19% 13% 32% 28% 6% 1	360
	11th to 20th	Night	18% 7% 30% 33% 11% 1	360
	21st to end	Night	19% 9% 27% 32% 13% 1	360
July	1st to 10th	Night	13% 7% 31% 32% 16% 1	350
	11th to 20th	Night	15% 6% 28% 35% 15% 1	348
	21st to end	Night	12% 5% 34% 34% 13% 1	407
August	1st to 10th	Night	14% 4 26% 36% 18% 2	537
	11th to 20th	Night	11% 6% 23% 34% 22% 3	534
	21st to end	Night	16% 8% 31% 26% 17% 2	683
September	1st to 10th	Night	14% 8% 31% 28% 16% 2	720
	11th to 20th	Night	21% 8% 27% 26% 15% 3	720
	21st to end	Night	23% 11% 23% 27% 14% 2	720
October	1st to 10th	Night	27% 15% 25% 21% 10% 2	720
	11th to 20th	Night	29% 18% 30% 15% 7% 1	720
	21st to end	Night	34% 17% 30% 16% 4	792
November	1st to 10th	Night	29% 17% 29% 19% 5% 1	740
	11th to 20th	Night	26% 24% 28% 16% 6%	760
	21st to end	Night	31% 20% 28% 17% 4	760
December	1st to 10th	Night	33% 20% 34% 10% 3	760
	11th to 20th	Night	27% 23% 33% 14% 2 1	760
	21st to end	Night	33% 19% 30% 14% 3	836

Page generated at 2024-03-31 06:08:55. Version ac07

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