Blythe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blythe clear sky chart from 2005-11-06 to 2024-07-31.

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	2 2 1 2 2 2 2 2 4 5% 76%	90154
	Night	2 2 1 2 2 2 2 2 4 5% 75%	89880
Transparency	Day	12% 2 4 12% 26% 44%	89881
	Night	13% 2 4 12% 25% 44%	89675
Seeing	Day	3 5% 17% 34% 31% 10%	14990
	Night	3 3 15% 42% 33% 4	25236

By Month

Percentage Cloud Cover SW (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	3 4 1 3 3 3 3 2 4 6% 67%	2858
	11th to 20th	Day	2 2 1 4 2 3 2 2 4 6% 71%	2860
	21st to end	Day	7% 4 2 5% 3 3 3 4 6% 7% 58%	3306
February	1st to 10th	Day	3 3 1 2 2 2 3 3 4 5% 72%	1900
	11th to 20th	Day	2 2 1 3 3 2 3 3 5% 7% 69%	1850
	21st to end	Day	3 2 1 4 2 2 4 2 4 6% 69%	1570
March	1st to 10th	Day	2 1 1 2 2 1 2 2 4 6% 77%	3213
	11th to 20th	Day	3 3 1 4 2 2 3 3 5% 7% 66%	3490
	21st to end	Day	2 1 1 2 2 2 3 2 4 6% 77%	3825
April	1st to 10th	Day	1 2 1 2 2 3 3 3 4 7% 73%	2152
	11th to 20th	Day	1 2 1 1 2 1 2 2 3 4 82%	2249
	21st to end	Day	1 1 1 1 1 2 1 3 5% 84%	2403
May	1st to 10th	Day	1 1 1 1 2 3 90%	4110
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 89%	4071
	21st to end	Day	1 1 1 1 2 93%	4477
June	1st to 10th	Day	1 1 2 1 1 1 1 2 4 85%	2470
	11th to 20th	Day	1 1 1 1 1 1 2 92%	2470
	21st to end	Day	1 2 1 1 1 1 2 1 2 3 85%	2470
July	1st to 10th	Day	1 2 1 2 2 2 3 3 4 5% 77%	2470
	11th to 20th	Day	2 2 1 2 2 2 2 3 6% 8% 69%	2470
	21st to end	Day	4 3 2 4 4 4 3 4 6% 8% 59%	2677
August	1st to 10th	Day	1 2 1 3 2 3 3 3 4 6% 72%	2318
	11th to 20th	Day	2 1 1 3 2 3 3 2 5% 6% 73%	2122
	21st to end	Day	3 2 1 2 2 2 2 2 3 6% 74%	2376
September	1st to 10th	Day	2 2 1 3 2 3 3 3 4 5% 73%	2016
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 87%	1980
	21st to end	Day	1 1 1 2 1 1 2 2 3 4 81%	1980
October	1st to 10th	Day	2 2 2 1 1 2 2 3 5% 79%	1980
	11th to 20th	Day	1 1 1 1 2 1 1 2 4 86%	1922
	21st to end	Day	1 2 1 1 2 2 2 4 84%	1980
November	1st to 10th	Day	1 2 1 2 2 3 1 3 4 81%	1674
	11th to 20th	Day	1 2 1 2 2 2 3 2 3 5% 77%	1710
	21st to end	Day	3 2 1 4 2 2 2 2 3 6% 72%	1710
December	1st to 10th	Day	3 3 1 4 3 3 3 3 4 7% 65%	1710
	11th to 20th	Day	2 2 1 5% 4 4 4 4 8% 8% 57%	2169
	21st to end	Day	6% 3 2 4 2 3 4 5% 6% 8% 57%	3146
January	1st to 10th	Night	2 2 1 3 3 3 3 3 4 6% 71%	4097
	11th to 20th	Night	2 2 1 3 2 2 3 3 4 7% 72%	4110
	21st to end	Night	9% 3 1 4 3 3 3 3 5% 7% 59%	4362
February	1st to 10th	Night	3 3 1 4 2 2 3 3 3 6% 70%	2280
	11th to 20th	Night	4 3 1 3 2 3 3 2 4 5% 70%	2218
	21st to end	Night	3 3 1 3 2 3 4 3 5% 6% 67%	1884
March	1st to 10th	Night	1 1 1 2 2 2 3 3 4 7% 74%	3658
	11th to 20th	Night	3 3 1 4 2 3 3 3 4 6% 66%	3490
	21st to end	Night	3 2 1 2 2 2 3 3 5% 8% 70%	3828
April	1st to 10th	Night	1 2 1 3 2 2 2 3 5% 6% 74%	2024
	11th to 20th	Night	1 2 1 2 2 2 2 2 2 3 83%	1879
	21st to end	Night	1 1 1 1 2 1 3 3 86%	1777
May	1st to 10th	Night	1 1 1 1 2 3 91%	2860
	11th to 20th	Night	1 1 1 1 1 1 1 3 4 87%	2834
	21st to end	Night	1 1 1 1 1 2 94%	3110
June	1st to 10th	Night	1 1 2 1 2 1 1 3 3 85%	1710
	11th to 20th	Night	1 1 1 1 1 2 1 3 90%	1710
	21st to end	Night	1 1 1 1 1 1 1 3 4 85%	1710
July	1st to 10th	Night	1 1 1 2 2 2 3 5% 6% 77%	1710
	11th to 20th	Night	2 1 1 3 3 3 4 3 6% 6% 69%	1710
	21st to end	Night	2 2 1 3 4 2 3 3 6% 9% 64%	1872
August	1st to 10th	Night	1 1 2 1 2 3 3 5% 7% 75%	1617
	11th to 20th	Night	2 1 1 2 2 3 4 2 5% 6% 73%	1780
	21st to end	Night	2 1 2 2 2 3 2 5% 7% 75%	1980
September	1st to 10th	Night	2 1 1 2 2 2 2 2 4 6% 76%	1944
	11th to 20th	Night	1 1 1 1 1 1 1 2 4 86%	1980
	21st to end	Night	1 1 1 2 1 1 1 2 3 3 84%	1980
October	1st to 10th	Night	2 2 1 2 2 2 2 3 3 4 77%	1980
	11th to 20th	Night	1 1 1 1 2 2 1 2 3 87%	2038
	21st to end	Night	1 1 1 1 2 2 3 4 84%	2376
November	1st to 10th	Night	1 2 2 1 2 2 2 3 5% 79%	2400
	11th to 20th	Night	1 2 1 3 1 2 2 2 3 4 78%	2470
	21st to end	Night	3 2 1 4 2 2 3 3 3 5% 72%	2470
December	1st to 10th	Night	3 4 1 3 2 2 3 3 4 6% 67%	2470
	11th to 20th	Night	4 4 1 5% 3 4 3 3 5% 7% 60%	3041
	21st to end	Night	5% 3 1 3 3 4 4 3 5% 7% 62%	4521

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	19% 4 5% 13% 37% 22%	2859
	11th to 20th	Day	17% 3 5% 27% 32% 16%	2860
	21st to end	Day	25% 4 7% 15% 32% 16%	3306
February	1st to 10th	Day	16% 2 5% 14% 28% 36%	1900
	11th to 20th	Day	15% 2 4 15% 29% 34%	1860
	21st to end	Day	17% 2 5% 15% 30% 31%	1570
March	1st to 10th	Day	10% 2 3 17% 37% 31%	3213
	11th to 20th	Day	15% 4 5% 19% 31% 25%	3490
	21st to end	Day	10% 3 3 14% 43% 27%	3825
April	1st to 10th	Day	12% 2 3 11% 27% 44%	2152
	11th to 20th	Day	9% 1 2 6% 26% 55%	2252
	21st to end	Day	6% 1 2 8% 28% 55%	2403
May	1st to 10th	Day	4 1 3 7% 23% 62%	4110
	11th to 20th	Day	4 1 2 4 21% 68%	4074
	21st to end	Day	3 1 3 18% 74%	4477
June	1st to 10th	Day	7% 1 1 4 18% 69%	2470
	11th to 20th	Day	4 1 1 2 12% 81%	2470
	21st to end	Day	8% 1 2 4 10% 75%	2470
July	1st to 10th	Day	11% 3 4 7% 13% 63%	2406
	11th to 20th	Day	12% 5% 6% 17% 27% 32%	2401
	21st to end	Day	21% 6% 8% 19% 21% 25%	2536
August	1st to 10th	Day	15% 3 5% 11% 24% 43%	2303
	11th to 20th	Day	12% 4 5% 12% 30% 36%	2122
	21st to end	Day	14% 3 4 11% 29% 40%	2376
September	1st to 10th	Day	15% 3 5% 12% 22% 43%	2016
	11th to 20th	Day	6% 1 2 6% 20% 64%	1980
	21st to end	Day	9% 2 3 7% 16% 63%	1980
October	1st to 10th	Day	11% 1 4 10% 23% 51%	1980
	11th to 20th	Day	6% 1 2 7% 23% 60%	1922
	21st to end	Day	8% 1 3 7% 24% 56%	1980
November	1st to 10th	Day	10% 1 3 12% 29% 45%	1674
	11th to 20th	Day	12% 2 2 12% 27% 44%	1710
	21st to end	Day	16% 2 4 11% 31% 36%	1710
December	1st to 10th	Day	22% 2 4 17% 26% 30%	1710
	11th to 20th	Day	21% 5% 9% 23% 29% 14%	2168
	21st to end	Day	22% 5% 8% 21% 29% 15%	3146
January	1st to 10th	Night	16% 3 4 14% 31% 32%	4097
	11th to 20th	Night	15% 2 4 23% 36% 21%	4110
	21st to end	Night	24% 4 8% 16% 26% 22%	4362
February	1st to 10th	Night	17% 2 4 12% 24% 40%	2280
	11th to 20th	Night	19% 2 3 13% 24% 39%	2219
	21st to end	Night	19% 2 4 12% 25% 37%	1884
March	1st to 10th	Night	12% 3 4 17% 36% 29%	3658
	11th to 20th	Night	17% 4 5% 16% 30% 29%	3490
	21st to end	Night	12% 3 4 13% 39% 29%	3828
April	1st to 10th	Night	13% 2 4 10% 28% 43%	2024
	11th to 20th	Night	10% 1 2 7% 23% 56%	1879
	21st to end	Night	6% 1 2 8% 25% 57%	1777
May	1st to 10th	Night	4 1 2 7% 21% 66%	2860
	11th to 20th	Night	4 1 2 5% 16% 71%	2835
	21st to end	Night	3 1 4 17% 75%	3110
June	1st to 10th	Night	8% 1 1 3 18% 68%	1710
	11th to 20th	Night	4 1 1 2 13% 80%	1710
	21st to end	Night	6% 1 2 4 8% 78%	1710
July	1st to 10th	Night	9% 3 4 6% 14% 64%	1665
	11th to 20th	Night	15% 3 6% 13% 27% 36%	1656
	21st to end	Night	15% 5% 8% 19% 24% 29%	1773
August	1st to 10th	Night	10% 2 5% 13% 22% 48%	1608
	11th to 20th	Night	13% 3 5% 13% 26% 40%	1780
	21st to end	Night	10% 3 4 11% 27% 45%	1980
September	1st to 10th	Night	12% 3 5% 13% 21% 47%	1944
	11th to 20th	Night	7% 1 2 6% 19% 65%	1980
	21st to end	Night	7% 2 3 8% 16% 64%	1980
October	1st to 10th	Night	12% 2 3 9% 20% 53%	1980
	11th to 20th	Night	6% 1 1 7% 19% 65%	2038
	21st to end	Night	7% 2 3 7% 18% 62%	2376
November	1st to 10th	Night	11% 2 2 9% 24% 53%	2400
	11th to 20th	Night	13% 1 2 8% 24% 51%	2470
	21st to end	Night	17% 2 3 11% 25% 43%	2470
December	1st to 10th	Night	20% 2 4 14% 23% 37%	2470
	11th to 20th	Night	24% 3 6% 14% 29% 25%	3041
	21st to end	Night	22% 3 6% 17% 32% 19%	4521

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	10% 6% 20% 40% 23% 1	270
	11th to 20th	Day	7% 4 17% 40% 30% 3	270
	21st to end	Day	5% 8% 26% 30% 25% 7%	392
February	1st to 10th	Day	5% 9% 23% 29% 25% 9%	460
	11th to 20th	Day	6% 9% 25% 32% 24% 4	455
	21st to end	Day	6% 11% 29% 37% 14% 3	382
March	1st to 10th	Day	5% 11% 25% 35% 21% 3	460
	11th to 20th	Day	6% 9% 19% 32% 26% 8%	460
	21st to end	Day	5% 14% 28% 33% 16% 5%	506
April	1st to 10th	Day	4 8% 22% 36% 23% 7%	460
	11th to 20th	Day	2 11% 30% 32% 18% 6%	452
	21st to end	Day	1 10% 27% 30% 23% 8%	460
May	1st to 10th	Day	2 7% 23% 33% 27% 9%	463
	11th to 20th	Day	1 6% 23% 35% 27% 8%	488
	21st to end	Day	1 5% 25% 36% 25% 8%	529
June	1st to 10th	Day	1 3 14% 35% 36% 10%	490
	11th to 20th	Day	1 2 18% 35% 30% 14%	490
	21st to end	Day	1 1 10% 42% 35% 11%	490
July	1st to 10th	Day	7% 37% 41% 14%	486
	11th to 20th	Day	3 3 34% 44% 16%	484
	21st to end	Day	4 1 3 26% 46% 20%	528
August	1st to 10th	Day	2 4 34% 40% 19%	447
	11th to 20th	Day	2 4 28% 45% 21%	437
	21st to end	Day	2 5% 27% 43% 23%	495
September	1st to 10th	Day	3 1 9% 27% 43% 17%	450
	11th to 20th	Day	2 1 9% 34% 41% 14%	450
	21st to end	Day	2 3 13% 26% 41% 14%	450
October	1st to 10th	Day	3 4 16% 33% 35% 11%	450
	11th to 20th	Day	2 2 14% 35% 36% 11%	392
	21st to end	Day	2 4 15% 29% 39% 12%	297
November	1st to 10th	Day	1 4 14% 44% 30% 6%	270
	11th to 20th	Day	3 3 14% 41% 31% 8%	270
	21st to end	Day	2 6% 18% 39% 28% 7%	270
December	1st to 10th	Day	5% 2 17% 42% 29% 4	270
	11th to 20th	Day	3 18% 46% 30% 3	270
	21st to end	Day	7% 7% 20% 40% 22% 4	297
January	1st to 10th	Night	4 3 16% 45% 29% 3	760
	11th to 20th	Night	4 3 18% 44% 28% 3	760
	21st to end	Night	7% 5% 20% 42% 24% 2	836
February	1st to 10th	Night	4 4 20% 42% 27% 3	760
	11th to 20th	Night	5% 4 21% 46% 21% 2	744
	21st to end	Night	5% 6% 24% 45% 18% 3	628
March	1st to 10th	Night	4 4 25% 46% 19% 2	760
	11th to 20th	Night	3 5% 19% 39% 29% 5%	760
	21st to end	Night	2 6% 25% 43% 22% 3	836
April	1st to 10th	Night	2 4 23% 45% 24% 2	760
	11th to 20th	Night	1 5% 27% 41% 22% 3	751
	21st to end	Night	1 5% 23% 44% 24% 3	637
May	1st to 10th	Night	1 5% 23% 45% 24% 2	570
	11th to 20th	Night	1 3 22% 43% 30% 1	561
	21st to end	Night	1 3 23% 45% 25% 2	617
June	1st to 10th	Night	1 2 14% 52% 29% 2	570
	11th to 20th	Night	1 1 15% 49% 32% 2	570
	21st to end	Night	1 1 9% 46% 40% 3	570
July	1st to 10th	Night	1 4 46% 47% 2	555
	11th to 20th	Night	3 1 3 40% 49% 4	552
	21st to end	Night	2 1 4 36% 53% 5%	624
August	1st to 10th	Night	1 1 3 39% 51% 4	543
	11th to 20th	Night	2 4 29% 58% 8%	712
	21st to end	Night	3 4 28% 56% 9%	792
September	1st to 10th	Night	1 1 8% 32% 50% 8%	720
	11th to 20th	Night	1 1 5% 36% 49% 8%	720
	21st to end	Night	1 1 10% 37% 45% 6%	720
October	1st to 10th	Night	2 3 15% 42% 35% 3	720
	11th to 20th	Night	1 1 12% 45% 38% 4	720
	21st to end	Night	1 3 12% 41% 35% 8%	792
November	1st to 10th	Night	2 2 13% 46% 32% 6%	740
	11th to 20th	Night	3 1 12% 42% 35% 7%	760
	21st to end	Night	4 3 16% 43% 29% 5%	760
December	1st to 10th	Night	6% 2 15% 45% 30% 2	760
	11th to 20th	Night	6% 2 17% 44% 30% 2	760
	21st to end	Night	5% 4 19% 46% 22% 3	836

Page generated at 2024-07-28 06:52:14. Version ac07

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